Need help diagnosing a problem...

sounds like a possible head gasket.

Might have bent a pushrod with that rocker needing constant readjustment. A collapsed lifter will do just that if an exhaust lifter is the problem. The intake valve will let the mixture in, then it's ignited, but the exhaust valve doesn't open to let the exhaust out. When this happens, the intake pushrod can be bent, trying to open the valve against the pressure. When it does bend, it doesn't open the valve either, and you have a dead miss. A wiped cam lobe may be the initial cause if the lifter quit spinning. It will wear out the lifter bottom and open a new oil hole in the bottom of the lifter, collapsing it from loss of oil pressure.

Better tow it.