Yeah, don't strip the block side. That's a major pain in the ass to fix. FSM says 12-15 ft-lbs on that bolt. I'd go find some 12mm (inside diameter) copper washers and try again. 1/2" will work, too.

You're not out of the woods yet on the coolant lines. They don't pressurize until you've reached operating temp. That'll be around 13-19psi. The oil line was prob seeing 60psi at idle, though.