[Foober223]

Your co-founder wants to profit from 11 months of your life and leave you in the gutter. 11 months is about 2% of your entire adult working life.

Don't give in to anything. The guy is a crook.

He should have proposed the paltry 3% before you dedicated 11 months of your life on the business.

At the very least he should offer to pay you a market salary for the 11 months you worked. He could take out a loan to pay you.