I'm not at all surprised you were having trouble at 80lbft, head gasket will likely be no better than scrap now though, ie weakened.
They need torquing up to 120lbft, that's what I do it to, using a victor reinz group a Yb 0611, part number now is 27380 00, as this is a fibrous gasket leave at least 4 hours then retorque, or overnight is fine.
It is 100% vital that the studs do NOT bottom in the block, each hole needs clearing/tapping and depth checking, the if necessary trim a few mm from the stud if needed.
The studs have a shoulder that sits in the very small area around the actual hole, this absolutely must sit on the block and not be proud.
The studs just need nipping up with pliers nothing more so they don't move.
Lube the top threads with 10W40, not swimming just damp, the refit etc the head.
tabetha