Yes, those first few days even a week or two can be rough. It's pretty much impossible to not have those "good times" thoughts appear. Try to just shoo them away as much as possible and not dwell because they are not reality - well they are and they aren't.
Fun concert and being abandoned for a week. Needing support and finding someone too high to really talk to vs a relaxing weekend, that's the reality.
He has run off because he doesn't want recovery, it's pretty much that simple. Nothing to do with you personally. You represent the "normal" the "i should stop being a drug addict" - that's not what he wants, he might want you and a normal life but he can't have that and the drugs - so he chooses the drugs, there aren't that many addicts that wouldn't.
If there were, these forums would not exist.
You are doing well, try not to isolate too much, I know it's tempting, who wants to go out and struggle to put on a brave face, but it can really make you feel better, even if you don't want to socialize it's better to drive over and buy yourself a cup of coffee and even sit and drink all or part of it in a coffee shop than to stay home alone too much.