OP, it is really challenging to dial it back. I have been doing my best to keep things reasonable with my OSO, because his wife just recently told him (like 2 weeks ago) that she is not comfortable with us having a romantic relationship. This is after she said we could hang out, and spend time together, she knew there was some physical contact (kissing, cuddling, even some below the belt kind of contact, etc.). We have been seeing each other twice a week for the last 6 months. And then when he goes back to her to see how we might be able to move forward, she in fact dials it back herself. She knows full well what she is asking of him, and it is unfair, without going into a whole lot of details about why.
He is currently deciding what to do about that. His relationship with her was not strong in the first place, and they have significant communication issues to overcome. In the meantime, we know that we cannot move forward with having a sexual relationship unless she changes her mind, or he chooses to leave the marriage. Which sucks. But is reality. As far as romantic goes, sorry honey, but those feelings are already here and not going away. I can only promise not to act on them. Her reasons are valid. She entered into a monogomous marriage with him, and that is what she expects him to adhere to. He is really just making plans to get out as gracefully as possible and hoping to not mess up his kids.
AS far as your former GF goes, it sounds like she may not have told her her husband some things from her past and she is concerned about his reaction to that. That is her choice, and she will need to decide whether she can go there or not. But if she cant even tell him that you "used" to date her long ago, then perhaps she is not really ready to have a poly relationship yet, with this husband. Does he even know that she is bisexual? That she had been poly before? Those are all questions that need to be explored.
Good luck to you. I hope it works out for you.