Have you directly brought these issues to his attention? If you haven't...
I'd list the items that are bothering you most and how'd you like to have them resolved. Maybe run it by a trusted friend - someone who will be directly honest with you. Then, break the list into two categories - can live with it and can't live with it. For the former, make like a duck - let them roll off your back. Just shrug your shoulders, roll your eyes, and say 'Oh that <cofounder name> is silly'. For the later, I'd look to directly address your partner in a manner that is meaningful to him. If you come to some consensus, set ways to monitor it to see if things are improving.
After this, you will have accomplished 2 things. One, you took ownership of the situation in a mature and constructive manner. This helps, especially if things don't work out, since you know you gave it your best (read: less regrets). Two, you'll have a better idea of how likely things are to improve.
If you have done this and things are not working, then look at the options. Is it worth sticking it out? If not, list your options. Often times, the black and white options (quit cold turkey and stick it out) are not the best. Consider options like decreasing your role, decreasing his, bringing in a third party (e.g. a design guy), having distinct boundaries of responsibilities, or you taking over the design element.
If it is time to part ways, I'm sure you'll do it in a professional manner that doesn't burn bridges.
I'd list the items that are bothering you most and how'd you like to have them resolved. Maybe run it by a trusted friend - someone who will be directly honest with you. Then, break the list into two categories - can live with it and can't live with it. For the former, make like a duck - let them roll off your back. Just shrug your shoulders, roll your eyes, and say 'Oh that <cofounder name> is silly'. For the later, I'd look to directly address your partner in a manner that is meaningful to him. If you come to some consensus, set ways to monitor it to see if things are improving.
After this, you will have accomplished 2 things. One, you took ownership of the situation in a mature and constructive manner. This helps, especially if things don't work out, since you know you gave it your best (read: less regrets). Two, you'll have a better idea of how likely things are to improve.
If you have done this and things are not working, then look at the options. Is it worth sticking it out? If not, list your options. Often times, the black and white options (quit cold turkey and stick it out) are not the best. Consider options like decreasing your role, decreasing his, bringing in a third party (e.g. a design guy), having distinct boundaries of responsibilities, or you taking over the design element.
If it is time to part ways, I'm sure you'll do it in a professional manner that doesn't burn bridges.
Best wishes.