Cylinder pressure is leaking past either the rings or the valves. I would think it's probably running pretty roughly with that much difference among cylinders. Previous poster's suggestion is your next test. Oily plugs, blue smoke, lots of oil usage indicate worn-out rings. You can also do a leakdown test, and if you hear air escaping through the carb, that's an intake valve leak; through the tailpipe indicates exhaust valve leak.
With the readings you're getting, I'd be thinking rebuild.