Welcome to NeuroTalk, roscoe.

So glad you found us!
You've posed a really tough question. It was written beautifully, BTW.
I have a SIL who decided not to have children because of Mom-problems growing up, but I think she would have made a marvelous mother. (She has not been dxd with bipolar).
And then, as you pointed out and experienced first-hand, some women have children and then cause them so much misery. On top of that, you'd naturally worry if they'd inherit your same problems.
A relative was raised by a Mom who wasn't "there" for him. Her nightly yelling sessions with his Dad were the norm, and really traumatized him. She was sick a lot, too, and very needy.
However, he turned out to be a very thoughtful and compassionate husband to his wife, probably because of what he went through.
Where you are less affected by the bi-polar than your Mom and sister, and have a thorough understanding of how it affects you, perhaps you'd be able to raise children and be a good mother to them. Has your therapist weighed in on this question?
Best wishes to you, roscoe. I hope you will continue to post and let us know what you decide.