A good shop can repair a crack, but I don't know if it's worth it with this particular head. It sure sounds like your symptoms are a cracked head and if you weren't dealing with a commonly known symptom of a head that often develops issues, I may approach this differently.
I know it's a kick in the nutz, but that's where I would go before any additional time spent on diagnosing it.
Again, I'm no expert, but I'm a mechanical guy. That TJ that I owned that had the cracked head also locked up the engine on the interstate because of a cooling system failure. I repaired the hose, filled it up with water and drove it for another 50k miles with the same cracked head and no additional work to the engine until one day it started overheating at any speed over 55 mph and I sold it to a friend. To my credit, it was a sport with AX15 and a Dana 44 rear with 3.73 gears and 180k miles, and I let him have it for $3500. He had the head repaired and still drives it to this day as a second vehicle. He thinks he got a deal, and maybe I agree
. That jeep started me on a path in which I'm pretty sure I will never be without a TJ again.
But I digest, (family Guy reference) there really is only one way to rule it out...