My understanding is that vega will tell me how much my option price will change per 1% change in IV. My question now is, what does "1% change in IV" means. Is it an absolute 1% change, or a 1% change from the start point?
IV change is absolute. If it expands from .20 to .21 then it has increased by 1%
Implied volatility is very high now so trading from ...
Not fully answering your whole question, but a quick and dirty way to get the expected daily move by using the Implied Vol is to divide the implied vol by 16. (Taken from the Sheldon Natenburg book)
So an implied vol of 80% would imply that a 1 standard deviation move per day of 5%