Our friend in the SB is running 90/60 3bet 40 cbet 100% over the massive sample of 17 hands.
I know most guys in the pool that play somewhat frequent, so he likely won't turn out to be a nit or a regular.

OTF SPR is 4,5, "readless" I'm not sure whether pot/calling will be +EV as we need 45%, UTG will fold a lot since he has an RFI of >40 in UTG.

What's my line? Bet fold semi big or just shove and hope that he is as crazy as the stats make him look? Checking seems to be the far worst option, although usually with stacks as they are defiitely not a bad one, but as mentioned UTG just wont have enough hands to shove with.