Thanks for coming back and answering the questions we've had. I think the consensus is that it is not frostbite.
Here's what I think, and it's not a diagnosis. From examining the photos you posted and seeing all the tiny, little "warts" underlying the black, it sure looks like something my roosters have had in the past, although not anywhere near the extent of your boy's.
When I would scrape one of the black "warts", it would ooze a tiny bit of blood. Have you tried scraping a bit of those bumps to see what would happen?
I treated my roosters' black spots with Blu-kote, and they disappeared inside of a week. I doubt it's fowl pox, but if it is, it's very mild and dry fowl pox does usually clear up on its own. That you say this roo has had this condition before and it's spontaneously cleared up leads me to believe this is what may be going on.
I've spent a lot of time researching fowl pox, looking at pictures and no where did I see anything like what your rooster has. I think that's a very good thing. Wet fowl pox is a hideous think and can kill.
I recommend you try the Blu-kote on his comb. If it clears it right up, then we know it's just harmless black warts, and I sure would love to know what they're really called if anyone knows.
By the way, you said he's hard to handle. Wait until he roosts, and after it gets dark, grab him off his perch with a towel wrapped around his wings very snugly, and you will be able to totally have your way with the bratty boy.