compression test on one cyl is not enough data. Relative difference between cyls is what to look for.

Drain a little oil (or remove filter) and look for sparkles in the oil. If you spun a bearing, there will be glitter in there.

 

It should be no less than 100 PSI on any cylinder, with less than 10% deviation between. If you test 140 on each cylinder your engine is in top shape, as far as compression goes. A compression test isn't very useful without a cylinder leak test. But it looks like you already know that you need a new engine.

 

Man it definitely sounds like a misfire.
Oil down in there? Pieces of a plug? Valve cover gasket? Coil? All of the above?start with all of that but I guess it's too late now man sorry.
Did you try to retrieve the end of the plug? That seems like it will hurt your car very much.. try a maget tip in there or something please yo

 

'A compression test isn't very useful without a cylinder leak test.'

Untrue, in fact the compression test tells you easily as much. Leak testing is of no worth past say 20% leakage and a 20% leak is good for many years of driving yet. Leak testing is strictly for like drag cars where 5% makes or breaks you.

140 is actually some wear, these would be easily 170 or more and 190 better. 100 psi is a dead cylinder or one not providing any more power other than enough to reduce its' own drag to nothing.

Compression testing is worthless without throttle held wide open and ALL checked at 3-4 tests on each cylinder. The only way to be sure. Spark plugs all out doing it too.