I'm a little late to the game... why did you buy the car?

The compression numbers should all be within a bar. THere is more than just a "range", but they must all be close in the big range. And with low mileage, I'd expect them all to be around 10.

You need to do a leak down test and see where the leakage is..

Over heating...??? That's not good. How hot did you get it? Could have just warped valves and need a valve job. If you got it really hot, it's quite possible the rings have lost temper and gotten soft. You'd have to pull it apart and inspect the bores closely with accurate measuring equipment to know if re-ring is an option. Ussually, I'd say bore it and put o/s pistons in the block.

Michael