I think Toni put it perfectly. He isn't acting like a friend to you so don't be friends to him.
I think we're too nice for our own good sometimes. These events come up and the "polite" thing to do is to honor them.
Behaviour for both parties during a split can be strange. I would wake up way early before H and just sit in the living room. I listened to dance music on repeat (sometimes the same song) while I got ready for work. I was pulling away and was worried about what I'd do if he tried to cuddle in the morning. He started going for runs in the morning. (unheard of) drinking (crazy talk) none of this meant we were on drugs.
You were both unhappy. I suggest adding to your reading list How to Improve your Marriage without Talking about it. I've started that and it's really insightful.
Someone said here that if there's an OW in the picture you aren't even at the starting line and they're right. So just continue NC for YOU. It's for you to not feel vulnerable, to limit the times he can hurt or disappoint you, to gain back your emotional stability, to focus on you and not him, to stop thinking and analysing, and limiting what you know about his activities.
Read any and all threads on here that are similar to yours, I got a lot of insight that way. Use this thread to vent and people will tell you if your thought process is helpful or if you're being too hard on yourself.
He was a big part of your life for a very long time. So many things are changing. Give yourself a break while you're adjusting to all this change, and keep your head up. Take care of you even something small like a bubble bath can make you feel good.
