Could he be distancing himself from you because your sobriety has been easier for you?
Could he be angry and afraid because alcohol has a stronger control over him than he wants to admit?
You can only ask him.
Or say --you seem down, anything I can do to help?
I don't know what the man's thinking, nobody does. But, even in detachment and helping yourself, I still believe in caring, kindness, and compassion.
If he barks when you try to be caring, then yes, you have to back off and let him work it out all alone while taking care of YOU.