Buddy, what a wonderful family your husband has; to be able to go through such a horrific time, and be there to support him.
I've not been through re-hap myself or a family member, so I don't know how it all works. In my opinion, I would think your anger is normal. You thought you were helping with one thing (which, in reality you were) but, feel lied too. Who wouldn't feel angry.
If you were my sister, I would probably tell her I think she might be making it personal when it wasn't meant to be that way. He could very well have been embarrassed that he was medicating with alcohol, and that he "wasn't strong enough" to get through this awful time on his own.
As I said, I've not been through the rehab process but something tells me he wouldn't be shocked to hear that you are angry. Do you think it would be something he is willing to talk about when he returns? Try not to hold it back, otherwise you might grow bitter and angri(er) and that won't be good for either of you.
Try to enjoy his return, thank him that he went to seek treatment, In my opinion, you are blessed that he didn't want to continue the path.
Be well, please keep us posted!