That's awful.
He does have a point: you need to keep stimulating your mind. A payed job might not be overdoing it. Can you apply for disability?
Maybe (just maybe) a group of people with schizophrenia might be better better than one of people with BP. It depends on whether some would have BP-I with psychosis or not whether one would be more helpful than the other. Maybe there are two support groups.
I have had a bad experience with a BP support group. I felt like a crazy outsider. That doesn't help, obviously. The group on here is so big we've got all sorts, so it's different. But not all BP support groups are like the one I went to, I'm sure. It's just something maybe worth considering.
Of course your husband is being a jerk and your therapist is probably right you should focus on other things, ignore it. But I wouldn't compare it to a (physical) illness. Just say you need meds to function as well as possible and your therapist and psychiatrist know better.
Hopefully things will (soon) improve.