You should do a leak down on #2 if you don't have access to a leak down tester you can rig one up with the hose from your compression tester. Bring the engine to TDC#2 pressurize the cylinder and see where the air is going. Pin the throttle plate open and disconnect the intake tube and remove the oil filler cap. Bad Intake valve is gonna leak air back thru the throttle body. Bad Exhaust valve is gonna leak right out the tail pipe. Bad rings or a melted piston is gonna leak up thru the oil filler cap. A Head gasket leak bad enough to bring a cylinder down to 10 psi should push coolant out of the radiator. There's a few other possibilities also like cracked or warped head, cracked block ect. but i think any of them are gonna get you down to 10 lbs. It needs to come apart regardless of what you find. Best of luck with your project.