I have bipolar type 2. If I don't take my meds, by about 2pm I can feel a huge mood swing come on. I still go through hypomanic phases a few times a year and have learned how to direct that energy toward something useful, but I used to choose behavior that was not so...positive. Your husband is selfish and foolish. By not taking his meds he is choosing to damage your marriage. This is not an illness that can be solved with supplements, believe me I tried everything before finally accepting the fact that I may very well have to take my meds every day for the rest of my life if I want to live a fulfilling life.
I do know what he is going through, though. He's constantly ruminating about these issues, but doesn't have the skills to solve the problems. He can't find a way to fit in talking about them in a normal every day conversation, his brain is addled by the depression and exhausted by the mood swings, so that's why he asks to go out to dinner with you. It's safe. You won't be mean or yell.
You do need help, your husband needs help, and you have every right to insist that he gets it. One thing about the meds, the "normal" feeling they give you (if they are working right) makes you feel like your illness may not be real. At the same time, it's not unusual to not feel right about the feeling of being normal, which makes you want to go off of them. I am super super creative when I don't take my meds. I can write beautiful poetry for days, I wish I could explain how insanity can make you feel so alive, but I've never been adequately able to do so to a neuro-typical person. I miss that "alive" feeling, and it took a long time to come to terms with that fact.
Something happened to him in February, something traumatic. If this happens every year, he is working through some memories that he can't make peace with, it might be time for you to find out what it is.
I didn't read the other responses, this is just my take on your situation form what you wrote and from my own experiences with this disorder.