Just here to hand hold. It's such a fine balance between trying to do what they need and what they can tolerate. We have littlies so can't comment on whether it ends, (I hope it does!)
I wonder whether the playdates make him feel out of control because he feels like he can't escape the situation and like he is forced to do it? Maybe allowing him to set a timer for how long he wants to stay, or setting up a code for I want to leave might help reduce some anxiety?
Alternatively, could there maybe be some digital playdates if he likes playing online, or something that might have less pressure?
I've found that asking mine to list all the things that could happen before we go (to the point of extremity) helps me to sometimes see where their thoughts are leaning. Something like "i wonder if you will play with sticks? I wonder if there will be snail on the stick? I wonder if you might play pirates, and get so excited! What else might happen? And then when they start to talk, raise the game- I wonder if it might be a purple sword with green jewels, or it might be used to target enemies, or clatter on fences or bop someone on the head!" Then when they reveal their ideas, empathise with the emotion behind it and try and work out what a trigger might be.
For you, is there anything you can do to make the playdates more bearable? Is there someone else who can take him to them, or a way to smuggle cake in, or can you schedule them on a day you get to do the shopping early on your own afterwards or something?
Sending you lots of compassionate vibes here, it's a tough gig when other parents are involved too. Good luck!