I fully understand where you are coming from. I took him back after I found out A, until I found out he was back with her ( no contact with OW was one of my non negotiable condition for us to R),that's when I kicked him out. I think you need to look inside you what your boundaries would be, would you start as friends and go on friendly date? Only you can work this out.
As for me I'm not going slow with my STBXH as I can see that there will be no change in my situation. So I'm getting on with my life. No longer waiting for him, the door is just a tiny bit open!
