You have a lot of different questions in your post - I am only responding to the request for how to value the ESPP.
When valuing an ESPP, don't think about what you might sell the shares for in the future, think about what the market would charge you for that option today. In general, an option is worth much less than the underlying share itself. For the simplest example, assume you work at a public company, and your exercise price for your options is $.30, and you can only exercise those options until the end of today, and the cost of the shares on the public stock exchange is also $.30. You have the same 'strike price' as everyone else in the market, making your option worth nothing. In truth, holding that right to a specific strike price into the future does give you value, because it means you can realize the upside in share price gains, without risking any money on share losses. So, how do you value the options?
If it's a public company with an active options market, you can easily compare your $.30 strike price with the value of call options in the market that have a $.30 strike price. That becomes the value to you of the option (caveat: it is unlikely you can find an exact match for the terms of your vesting period, but you should be able to find a good starting point).
If it's a public company without an active options market, you will have to do a bit of estimation. If a current share is worth $.25 (so, close to your strike price), then your option is worth a little bit, but not much. Compare other shares in your industry / company size to get examples of the relative value between an option and a share. If the current share price is worth $.35, then your option is worth about $.05 [the $.05 profit you could get by immediately exercising and selling, plus a bit more for an option on a share that you can't buy in the open market].
If it's a private company, then you need to be very clear on how shares are to be valued, and what methods you have available to sell back to the company / other individuals. You can then consider as per above, how to value the option for a share, vs the share itself. Without a clear way to sell your shares of a private company [ideally through a sale directly back to the company that you are able to force them to agree on; ie: the company will buyback shares at 5x Net income for the previous year, or something like that], then the value of a small number of shares is very nebulous. There is an extremely limited market for shares of private companies, if you don't own enough to exert control.
In your case, because the valuation appears to be $2/share [be sure that these are the same share classes you have the option to buy], your option would be worth a little more than $1.70, if you didn't have to wait 4 years to exercise it. This would be total compensation of about $10k, if you were able to exercise today. Many people don't end up working for an early job in their career for 4 years, so you need to consider whether how much that will reduce the value of the ESPP for you personally. Compared with salary of 90k, 10k worth of stock in 4 years may not be a heavy motivating compensation consideration. Note also that because the company is not public, the valuation of $2/share should be taken with a grain of salt.
