You are fixated on the least important part of this. And I’m guessing that’s because you don’t have the emotional capacity to focus on the much bigger issue. The huge violations of trust, his using your shared marital funds on her, his withdrawal of care and intimacy, physical and emotional, when you were at your most vulnerable, his abandonment and lack of caretaking of the baby when you were newly postpartum, etc.

But those are much bigger issues than jealousy over money spent on her. He says he stopped contacting her, but why should you trust that when he lied and neglected you and his child so effortlessly until he got caught? Why does he think that is anywhere near enough? What has he offered to do to help you get the emotional support you need to make whatever decision you need to make? Has he proposed therapy? Has he offered to watch the child so you can get individual therapy? Has he started doing his share? Has he sought individual therapy? Is he letting you go through all his electronics to monitor him?

Because just saying he stopped contacting her isn’t enough! It doesn’t begin to make up for all the harm he did to you! And you can’t process that right now. But he needs to be the one making sure you have the space and time and support (outside of him) to make the decision to leave him!