Just look at the math for a sec. Ok, so it's more than a second...
Let's assume your $12/hr job is 30 hrs a week, that gives you an income of $18,720
(52 weeks * 30 hrs/week * $12/hr). That's not even your take home pay, which you'll likely pay about 25% of for taxes and other deductions like health insurance, so you're looking at just over $14k a year.
If we take that $14k from your $90k yearly expected expenses
($90k - $14k), that's still $76k you're spending each year more than you make.
With $1.2m total, you're looking at almost 16 years
($1,200,000 / $76,000/year = 15.7895 years) you can survive before your money completely runs out, including your retirement money, which doesn't include all the fees, fines, and taxes for withdrawing your 401k early.
Any returns you expect from your savings or investments aren't going to significantly change this math. You might get 1 more year, if the markets are continuously and reliably fantastic, but that's not much. And the more you take out of the investments, the less it earns, too, so you're looking at the definition of diminishing returns. And these returns might not even make up for the fees, fines, and taxes for withdrawing your 401k early I mentioned just a bit ago, so you might not even get more time than I calculated.
And this doesn't even account for emergencies. If your appliances go out, you're probably looking at around $1000 extra expense that you didn't account for. A washer or dryer might not be that much, but a fridge can easily be double that. And an AC or furnace can be even more. A water heater might run $500-800, but then you still have to pay for the labor, unless you get a tankless, then you're talking $1200 for the unit and even more for labor.
If your house gets damaged from a natural disaster or the roof just needs replaced, that's more money you're spending beyond your expected expenses. If a window breaks, which can happen just because of extreme cold, that's another expense. A kitchen fire can cost thousands to repair. A busted water pipe can damage multiple floors and cost thousands to clean up and fix.
Any remodeling is not going to happen.
What about your vehicle(s)? They aren't going to last forever. Even if you can do all the work yourself, the older they get, the more money it takes to keep them running. It also takes a lot of time to do the work. I kept one car to 185k miles and another to 215k miles, so I know that situation.
Yes, you're going to have to replace your vehicles at some point. And you aren't likely going to get a loan for a good replacement at less than $20k income. It doesn't matter how good your credit is, the bank knows that it can't squeeze more money out of you than you make. In fact, they will look at all your expenses vs. your income and see your $90k expenses for your $18k income and just flat out deny you the loan, as they run away screaming. Your debt to income ratio will be atrocious.
Sure, you could just pay in cash, but then that's going to reduce how long you can survive on your savings. Even if it's "only" $5000, that's almost a full month's expenses
($90k / 12 months = $7.5k/month). And $5k doesn't get you much for a car anymore. You're looking at a high mileage (90k-120k miles) 5-10 year old car at best, which is when major repairs start to crop up, so you're likely to start repairs on it within a few months.
I just spent almost $1000 getting a new set of 4 tires. The tire pressure sensors were out, so that added to the expense. And when they did the alignment, they found the rack and pinion steering and the tie rod ends needed replaced, so that's going to be another $900, unless I find some place less expensive or do it myself. Even if I do it myself, it's still $300-500 with the parts and another alignment, not to mention the likely +4-6 hrs to do it, since I've never done this before. And that's with me already having +90% of the tools, a spot to do it, quite a bit of experience under the hood, and watching a video of someone else doing it.
Your family might accidently, or purposely, grow. Your insurance isn't going to completely cover the birth, so that's more expenses. Not to mention another kid to feed, clothe, take to their sports events, and so much more.
Even if that doesn't happen, your current child is likely going to break an arm, leg, or have other hospitalizations at some point. I don't care what insurance you think you'll get, it's not going to cover everything. Nor is it going to cover the time you have to take off work to deal with it. And yes, even with a stay at home parent, the working parent is still going to have to take time off to deal with their kids at some point.
Next is schooling expenses. Even at public schools, you're expenses are going to be ever increasing. If the child takes sports, you're likely looking at a minimum of $1000 a year for equipment and other fess. That doesn't include stuff like trips, food/snacks/drinks, extra gas for the car, and so much more. Being in the band, a vocal, debate, or 100 other groups aren't free either.
Books aren't cheap, if they get lost or damaged. Graduation from high school usually includes a fairly expensive party. And you're going to have to figure out how to get Junior their first car. Do you make them buy it 100% themselves? Some people do, which isn't a bad thing, but that can lead to an unsafe and unreliable vehicle. And if they need a loan to get a decent car, you'll have to be on it as a co-signer, which your situation isn't going to help, as I mentioned earlier. Also, by this time, you'll be getting near to the end of your money. You might still have $330k in 12 years, but that'll be looking pretty tiny compared to what you're starting out with. (And don't forget that's only about 4 years of your expenses before you're completely broke.)
So in the middle of your child wanting to go to college, you'll be out of money. You won't be able to co-sign their student loans, you won't be able to help them pay their loans, and you'll be looking for your own money.
Forget going on vacation. You just can't afford it.
Since you won't have been adding much to your Social Security for 16 years, you won't have much to live off of. Your 401k will be drained, so you'll have to continue working until you die.
My dad worked as a welder for 20 years and as a farmer for over 20 years before that. His income from the welding job and the profit from farming wasn't much more than what you're going to making part time. After retiring at 65, he ended up working part time until either 72 or 76. He managed to squirrel away some "investment" he calls it, so now he's finally fully retired. He even helped his brother and some friends farming even after he quit his part time job to get some extra cash.
My mom had a variety of jobs, but one good one that paid really well. Until they canned everyone about 15 years ago and stole the retirement fund. She's now in her late 70's and still working, when she can find someone that'll hire her due to her age and health problems. She didn't even have a reliable job to officially retire from.
These are just 2 examples of the dozens of people I personally know and millions of people who work past "retirement age" to make ends meet. Don't be like them. Most of them didn't have a choice, with their health, employment opportunities (or lack thereof), lack of education, economic upheaval, and a thousand other reasons why they never made any real money, or lost what they did manage to make.
You do have the choice, so for you and your family's sake, don't take that option.
Is the stress of money problems a good trade-off for the stress of your current situation? Let me tell you, working a retail or food service position like Starbucks, as you mentioned, isn't without stress. You'll have to deal with the Karen's of the world when you don't get their order 110% correct. You'll also likely have to deal with under or un-educated managers who are unreliable, unreasonable, and unwilling to work with you.
You'll also have to deal with under or un-educated co-workers who are unreliable, unreasonable, and unwilling to work with you. There's a high turnover rate in these positions, and usually for a reason. And if you happen to stay at one job for long enough, you might have a manager that thinks you're trying to take their job and will get fired for that.
Is that stress worth $12/hr? Is that worth trying to stay within a budget that math has already shown isn't going to last you very long?
You'll probably think you can count on getting raises as the years go on. Sure, that's what everyone one else looks for. But at a low paying job like Starbucks and with you being part time, you're looking at 1.5-3% raises, if you get one at all. And they might even cap your pay at some point. And that's if they don't use excuses like "economic hardship", not performing as well as they'd hoped, not learning as much as you "should", having a few late arrivals or other bad marks on your record, or 100 other reasons they will give.
And that 3% of $12/hr doesn't even begin to cover the 3-5% increase in spending on the $90k you're currently doing. When people say "3% cost of living raise", they generally make more than they spend. And even 3% raises are just to keep you at your current level. That doesn't get you ahead. Not to mention that most pay raises are because of moving to another job, rather than just time-in-grade at a single position. Getting a new job takes time and money, and a fair amount of stress when you're trying to hide it from your current employer, as many people have to do. Getting fired simply because you're looking for another job is a real problem people face.
For over a decade, I wasn't doing as well as this Answer talks about. I tried to put myself through college on far less than $12/hr and on far less than 30 hrs/week.
Those old cars I talked about earlier? They were my daily driver and spare cars that I had at the same time. I'd bounce between them as one broke and I could afford to fix things. I ended up having to trash both, as the frames rusted completely through and they continued to require more repairs than I could keep up with.
I'm in a much better situation now, but it took over 5 years to pay off most of the credit card and personal debt I had racked up during that time and another 5 years to finish paying off student loans. Even still, I don't make as much as you are spending each year, and that's after me increasing my income around 2.5 times over the past 4-5 years.
While it's very appealing to retire early, you just don't have the money and situation combination to do it. As another Answer mentions, some people could retire now with the money you have, but not with your expenses. You'd have to severely reduce your yearly expenses to make the math work. If you increase the amount you get paid or the amount you work, that's great, but then is it really much different than what you're doing now?
Yes, I painted a pretty bleak, even fairly horrible picture of your future in this Answer. You might think I'm just trying to scare you and that it's not very realistic. Well, I am trying to scare you because it is all too realistic.