Have you done a compression check yet, or have you put a air hold fitting in the spark plug hole and see where the air is going? I am thinking with it missing that bad and only 1 cylinder not changing rpm when plug is pulled and no antifreeze smoking heavily out the exhaust it might not be a head gasket.
Stuck injector sounds like a good possibility. Possibly a cracked spark plug? Maybe worn camshaft or bent or broken pushrod/rockerarm? I just hate to see you pull a head and it not be the problem.