A good vet is a great thing, but a vet that doesn't do chickens in their office to me knows little about chickens, or any animal they do not routinely treat.
If you really want to save your Thor please try the natural route, I believe nothing is untreatable but death itself.
Mother nature is a much better doctor than most who have fancy degree's, god made all of us healthy, and our bodies capable of healing themselves, but with today's chemicals in our food/water/air supply and our pets food supply our immune systems are so low trying to rid ourselves of the crap we have little choice but to ingest, because its in everything! That we can do little to fight some of the diseases these man made chemicals/ hormones cause. Give him a chance the natural way. It's also much cheaper in the long run than a vet.
Why I know this is true is my 12 year old dog tigger, had a massive nasty cancerous tumor on her left front leg in the joint the vet removed it but couldn't get it all, said it would come back soon and kill her and it did, even before the stitches were out it was starting to grow again he gave her 5 months maybe, so I went to my herbalist Jen at Jens natural remedies, she gave me immune boosters, and several homopathics cost me not even 1/2 of the surgery charges, which were 350.00, took about a month and it is gone shrunk disappeared, and she is fine and that was over a year ago.......... so do as you wish, but if you love your rooster, get him some help so his body can help himself. Kim