OK so you dropped the 'cofounder' title and probably was fired from the company altogether, but you still retained stocks right? Stocks are legal term. He couldn't just take your stake away because he is a bro. If anything that sounds like a good deal to me. If he was right and your contribution to the company was insignificant, that won't even harm the exit value much, if he wasn't, bad for him much more than for you (because he will work his ass off in the process and you won't).