One other thought . . . . .
Since you have SOME compression in 1 and 4, I don't think it's a stuck valve. Maybe a warped one, but I don't think stuck. It's fairly easy to separate the diagnosis of a ring problem from a valve problem. I suggest pulling the (4) plugs, and applying a little motor oil (or MMO) through the plug hole onto the piston top and cylinder wall. Then, rerun your compression test. If the compression values come pretty even, the oil has sealed up the rings and they are likely the problem. If not, I'd be looking for two or more warped valves (or. . . maybe stuck) at the outer cylinders. If the head gasket is blown, I'd expect the compression to be lower than 60-70, so my guess is either you have worn rings that aren't sealing, or warped valves. If the overheating has happened before, the valves could very well be warpped from that event.
Just one man's thoughts on the matter . . . . .