I would 100% completely shadow him during playdates, like literally be there right with him and the other kid so you can intercept him. I know it won't mean a lot of interaction for you with the moms, but maybe they'll sit on the floor with you too. The closer you are to them, the faster you can intervene and intercept, and reduce the contacts. My style was to try to intercept the arm in mid swing/throw/pinch, or the head in mid bite, and keep a hold of it gently while making make eye contact and say firmly in a low, growly tone, "NOT OK. PLEASE be gentle, you can X instead" and give them an option based on what emotion I thought it was (anger, excitement, etc.).
I've spent many a playdate with younger toddlers on the floor with/between the kids to prevent such things from happening - hell, I've done it with my own kids when my daughter was going through a biting phase, I'd be right there with them while they were playing when I knew she was in a bitey mood. If he can't handle the interactions on his own, your only options are to eliminate the interactions, or to be right there on top of him while he's in the stage. I'd personally choose to be right there with him.
It's a tough phase for some kids, but he will grow out of it so long as you keep setting the limit and preventing as much as possible, and redirecting his emotion to a more appropriate expression. Good luck!
