You are taking the same risks as the founder and you being there is directly helping the founder raise funds and hire other engineers. Don't under-value yourself.
Your previous total comp was base + public/liquid stocks. You should compute the growth in valuation of those liquid stocks (if it was similar to FAANG stocks, its growth would have been 50%+) plus the return on investment of your savings. Add that to your total comp.
For your startup comp to beat this total comp, given your 1% stocks, compute backwards the valuation your startup has to achieve. Does it look feasible or too crazy? How long will it take?
Do market research to understand how much revenue and profits a public company in similar sector does to achieve that valuation and how much capital investment and tech innovation is needed to get to that. Ask questions to your founder boss, meet their investors to understand their thinking.
Very important to consider what happens if you quit before it got there. If you have to pay to exercise options, or your options get bought back by the founder at a discounted valuation etc. (some startups have started doing "stock appreciation rights" which are somewhat unfair) understand those for what they really are and factor that into your calculation. Understand how cap tables, dilutions, liquidation etc works and factor the risks into your calculation.
Finally, remember that founders get fired/replaced; your direct boss is going to be someone else very shortly (especially if the company grows fast) etc. so don't go by verbal promises. If you are looking to make millions, invest time and energy to understand and negotiate your employment contracts properly.