Time and proximity.
If you get frustrated with him, he'll sense it and be scared, expecting a beating.
Talk in low, soothing tones, don't raise your voice, even to shout to your wife or your kids.
Keep your movements slow and steady.
Don't ignore Max, but don't exactly pay attention to him, either.
Practice this for a couple of days, and I suspect that very soon you're going to have a dog coming up to you to check you out.
When he does that, don't move, just let him sniff you.
In other words, let him take it at HIS pace, not yours. He's the wounded, confused one. Let him sort it out that you're not a threat, you're a friend.
I did this with a dog some years ago. She was very timid around me. After practicing this for 2 days, she started sniffing at me, and getting closer. I could tell that she wanted to be friends. On the third day she very, very gingerly climbed up on the couch and laid down beside me. It went pretty fast after that.