Forgive me, Wildcat, for being so blunt, but are you over-analysing yourself about the group? Support groups can be great, but not all groups are going to work, depending on the make-up of people involved. Yours sounds like it's a group of people who, despite having bipolar in common with you, are otherwise in completely different life situations to yours. Is it giving you any learning to be observing how other people with bi-polar cope, when the challenges they are trying to cope with are foreign to you and vice versa?
My opinion: the group provokes the worst in you because you aren't getting anything from it and it's wasting your time. Time being something that you have precious little of, and any spare second you may be able to grasp you want to spend on your family or yourself, rather than with a group of people who have no concept of what it's like to be bipolar in a such a full-to-overflowing life.
I hear your anger and frustration. One of basic elements of a support group is that all participants feel understood and supported, and it doesn't sound as though you're feeling that way. So you've been, you've observed, and you've persevered at going and observing. I'm sure that you'd be happy to go, observe, participate in another support group with, as dumpling suggests, a better balance of giving and taking. A more even distribution of life situations, perhaps.
Again, just my opinion: take that 1-2 hours a week for the next couple of months and play with your children, go out with your husband, relax in a hot bubble bath -- any of which would probably give you more emotional benefit than this group is.
Your determination is truly wonderful, Wildcat, and you have an awesomely enormous heart :)