If a company is raising a pre-seed round to build a prototype, should the founder get paid a small salary?
If it means they can pay rent buy food then yes. Often a founder is asked to work for nothing A ramen salary (look it up paul graham of SV coined iy) goes a long way. If they don't want it you can always reivest it. Just an offer
Only if you are putting money into the round. Even then it is bad optics if you retain 90% of the equity.