Sounds to me he has embraced his sobriety....good for him!
But like you write, you are dealing with your thoughts and feelings.
I would support him wholeheartedly...
If I was sponsoring him I would give him a big time kudos. If he was in AA see if he has a big book and give the Family Afterwards a read. It's a bit dated but very upbeat.
Sometimes we keep our doubts to ourselves other times not....should you ask him if it's all for show? Probably not.
Put your focus back on your program...you deserve your own recovery and the joys that come from it. You are a very caring and loving person.