The only way you would need a piston/sleeve rebuild would be if you really toasted the engine (got it hot, and let it run that way for a while). The construction is pretty solid, lasts for quite a long time. Tends to be pretty tolerant of most brief lean runs.
If the engine gets hot when running, the best thing to do is richen it up a bit, then shut it down. Once it has been over-lean and gets hot, it will not recover to give you any reasonable rpm readings. Best to shut it down, wait 5 minutes or so, open the needle a bit from where it was, and start over.
The engine fit gets better with time... may feel looser .... but that is normal.
If it has zero compression, Id be looking at the head bolts and glow plug for a physical leak. The engine should still have a seal/fit up top. When warm, that should be noticable. The other thing that helps....... toss a 9x7 prop on it for a tank ... let it run a bit.
A cracked header coupler will really mess up the system/function if it allows gasses to excape. But your data looks ok
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