I don't have much to offer as you've already done a lot of diagnosing. I assume that you used the dye test in the coolant. I think that you've got it narrowed down, it's either a head or a head gasket. I would suggest that next you do a leak down test to determine which cylinder is the culprit. Then you'd have to remove the head and inspect for evidence of a leak.
Perhaps you know how to do a leak down but the test is accomplished by placing the piston at top-dead-center on the compression stroke and pressurizing the cylinder with an air compressor. In your case bottom-dead-center will work too, it's easier, the piston will naturally move there when you pressurize the cylinder. Just make sure that the valves are closed. Fill your radiator and watch it with the cap off. Give the test some time, like several minutes. I had a Subaru with a leaking head gasket and it took a few minutes for the cylinder to leak enough to start pushing out coolant. I didn't get bubbles but there was a big push of coolant. A big bubble would have appeared eventually. And of course I got results on the fourth cylinder (out of four) that I tested.