You are going to have to work very hard to detach and let go. I think your best bet is to continue trying to create good memories, and be as nice as possible. In an earlier post you asked for specific advice:

>>how the heck do I address things that will inevitably bring on tension in the house. <<

Detach and give space. He is in no position to work with you on any issues right now. He will be searching for ANY reason to validate what he's doing and will be seeking out any possible negatives in the marriage to latch onto.

>>I am trying to give him space but we still live in the same house and have a 4 year old so I kinda need to know what is going on.<<

No, you don't need to know. Consider him a "room mate" with his own life and start working your life, your child's and your own person schedule without him. Any questions will be perceived as invasive and controlling.

>>How do I approach money subjects without being controlling. One of the problems in our M is that I have always been controlling with the money<<

You only have control of your individual finances. What he has access and spends on her, or whatever else, you may not have too much control over, and he will use this as justification to move forward in the affair as well. I suggest you consider putting a little money in a safe place.... just in case.

{{{{hugs}}}}

There is no arriving, ever. It is all a continual becoming.