Nothing could have prepared me for his relapse (and I thought I was!). But also, nothing taught me more than his relapse.
What I learned was: listen when he says he needs to go slow..... and his recovery will always come before me because without it, there is no us.
Recovery is so individualized but your friend seems to be doing well. Let him continue to do well and be confident in his ability to get through life's stressors without drinking. That may take a while.
The longer things take to come together, the longer it takes them to fall apart.