How about trying this - pick a specific day this week or next and pick something to do - even if it is only to go to a coffee bar - and as soon as S has gone to school go do it before you get thinking about things. I had to do this about 2 weeks after H left. My friend gave me the idea. I picked a day and wasn't allowed to back out of it and I set my alarm and I got me and S ready and went to town on the train - I had never taken S on public transport before - I had made a list of things to buy - one of them being R self help book - and I did it and came home. I felt so much stronger when I got home and H was amazed when he found out too.
The support group sounds like a good idea. We went to one when we were going through IVF stuff. It really helps to talk to people in the same sitch.
My S does have lots of little friends now yes. He has been to two parties in the last couple of weeks and has another one soon. It's really sweet.
I think your H mentioning things to do the home is a sign he's coming out of his alien phase too. My H is doing the same. He has started mentioning things that need doing in the garden whereas when we were separated he didn't care about it at all and I had to struggle with it. I think they like to feel in control because they maybe didn't feel in control before they left - think that is why they don't like it if we mention future but it is OK for them to.