Well, one possible case scenario is that OP’s contract does not allow his cofounder to fire him, or fully vests if he does. He can this tell his cofounder to pound sand and his cofounder will have to realize that his options are 40% or 0%. If he believes the company has a bright future, he’ll take the deal. There’s a very real chance OP gets much more than 3% or 6%.

Or there’s something better that I can’t think of because I’m not a lawyer who deals in this and don’t know the specifics.

It’s just bad to give really any advice here, which is part OP’s fault really because he should not be asking a lawyer rather than Internet randos.