Yes, this is a big adjustment period. He is going through withdrawal of the "OW drug". It will take a long time. He got a "high" with her. I remember laying down A LOT. Depressed a LOT. Leave him alone if you can. I know it is hurtful, but he just needs to get through this. It is critical he does not contact OW at all now. If he does, this moodiness will start all over again.
By the way, it is a GREAT sign he wants to get together with old friends. That was the old life he left behind when he started making bad decisions. He avoided those old friends while having the affair.
Just be the best you that you can be. Try not to have any big relationship talks right now. Showing him you are thinking about him (like the OW probably did) would be good- emailing, texting, calling, etc. Plan some trips with your H- maybe a short drive somewhere to have a picnic, or go to a live concert, etc. Anything fun and different to show that things will be different THIS time with you two. And, it will keep his mind off of the OW and back on you.
