Is the #5 spark plug wet with gas?
A compression test will only tell you what you already know. No compression in cylinder #5.
My compression tester has a quick disconnect in the hose which just happens to have the same male air fitting as my air compressor hose.
I turn the pressure from my compressor way down with a regulator and apply air pressure to the spark plug hole.
With the piston at top dead center with the valves closed, listen for air escaping though the carburetor, exhaust pipe, or into the crankcase.
That will indicate bad intake valve, bad exhaust valve, or bad rings respectively.
Good one. I forgot about that.
I found a hung up exhaust valve on a '64 Galaxie that way. Air was blowing out the tailpipe.
