I do not want to rush him or back him into a corner, yet I do not want to sacrifice any more time/attention/raw emotion on a man who might not genuinely be prepared for the task of rebuilding a marriage with me.
It's not really about wasted time. It's about finding out whether or not your WH is really willing to reconcile and to abide by the boundaries of marriage.
I get it. No one was more surprised than me to find that I was willing to reconcile after my WH's really florid adultery. It never even occurred to him that I might take him back, so he thought he needed to find a soft place to land with the last of the three OW. And just like in your case, she'd already exploded her own home situation due to their future-faking, so there was enormous pressure for him to follow through. Here's what I told him though... "The OW is not a child and she did not engage in any behavior that she didn't fully choose. She knew the risks of cheating in her marriage. She made a free choice to cheat anyway."
I gave him literally NO TIME to end it with the OW. He had to make his decision on the spot, and I let him know that there would be no changing it. He had to be either "all in" or "all out" of the marriage.
Now bear in mind that I had already told him I was divorcing him on DDay and that he had already asked me for a month "to prove that he could be trusted". Of course, he had then used that month to try and let the OW down gently and ease out of contact with her, despite his initial promise to go complete NC. 
So, he had already abused the chance he'd asked for and I was fed up. I meant what I said, "choose, choose now, and know that your choice is permanent".
Here's the thing with the "Pick Me Dance". It's basically triangulation. It feeds the drama. It feeds the affair. Your WH has two women competing for his grand self, and don't think for even a minute that even while he whines about how much guilt he has that there isn't a part of him just digging it.
Meanwhile back at the ranch, in order for real healing to occur in R, you can't feel like there was any real contest. You must be number one, because there's already so much hurt and trauma to recover from. So, if he can't pull his head out of his ass to let you know that you're what he wants, the recovery becomes almost impossible. Every day he leaves you wondering is more damage piling up, until the pile is insurmountable.
I know it's scary to take the risk of putting your foot down. There's no way to predict the outcome of that. But... as long as he's in contact with the OW, he's still cheating and the affair is still alive. You can't recover a marriage while the adultery is ongoing. The adultery must stop.
During an affair, the allegiance of the WS changes from their spouse to the AP. So, they do feel some responsibility for the future-faking and weasel words when the AP loses their home dynamic. It's not like most of these AP's don't know for a fact that the cheater is married though. So, they knew the risks. They are not innocent, and in order for the cheater to break their hold on his guilt, he needs to see that they AP is just as responsible for the consequences of her choices as he is. Essentially, there's some survivor's guilt to deal with when one marriage implodes but the other does not. So, you have to disarm that by reminding him that the OW is a grown woman who made adult choices all along. She's not an innocent. She doesn't need rescuing. And outcomes after infidelity are not guaranteed.
Your outcome is not guaranteed either. But you have to know where he stands and whether he's willing to work for recovery. If you let him turn you into a door mat, he'll never respect you enough to do the work required anyway.
I'm sorry. It's so scary, I know. But you can't be the third wheel in your own marriage.
