its time to renegotiate your role, or leave. think of it like refinancing a mortgage.

set up a meeting a present a roadmap forward that would make you happy. put yourself in the real co-founder role and get what you want. may include more equity, a plan to grow the team, different office layout, whatever u need. offer him this roadmap forward, or you will leave (1 month notice would be honorable).

if you leave you will find better opportunities and more pay, guaranteed. you have a proven track record and good attitude