[akanet]

Bluntly, if you have to ask on hacker news, you are not equipped to handle this situation and should look to either exit or enlist more capable help. Your quandary is so contingent on the specifics of you, your cofounder, and the competing directions of the company that no good advice regarding a direct action to take is possible here. That you would ask in this forum is a very bad sign that either communications have broken down or you have not attempted a conciliation.