
I'm sure I don't need to tell you how rough the lockdowns have been on those with mentally ill relatives for whom they care - you're living it, as you describe. In a way you can take comfort in the fact he's back home because it means he's not spiralling out of control without anyone at least watching over him as might happen if living alone. If he doesn't come home for a day or two...you'll definitely notice and start phoning around. If he turns to drugs, you'll notice, etc. So just being home, even if he's "getting worse", is still in some ways a blessing - just be careful not to helicopter-parent a 32-year old!
If his anxiety and panic episodes are reaching frightening proportions, can I ask if he's been prescribed any meds to help combat the symptoms...and does he freely take them, or he dislikes them? De-stigmatizing the medication was one of the biggest hurdles for some caretakers - and sometimes you have to treat it the way you'd treat trying to get a 9-year old to take a multivitamin (or cod liver oil). If he's not been prescribed anything, there are over the counter things a little stronger than chamomile that can still help soothe the fraying nerves (and may also help his parents!) - but they're not as useful once the proverbial actually hits the fan.
Hang in there, focus on the positive, and consider at what point you'll be willing to calm him and say "the pandemic is pretty much over" whether that means life changes or not.