Hello,
Well, there really is no other alternative honestly. If it goes untreated, the infection will travel up his tail, & he will lose his entire tail & can get very sick from a system infection.
No peroxide. I do not know why people still recommend it, but it is not safe for reptilian use. Continue with the diluted betadine daily, along with the neosporin or polysporin, daily. There is also a product called thermazene that you can get which is extremely good & might help out more than the ointment. If you see dead tissue, try to GENTLY scrub that off with a soft toothbrush just to clear it off of the area to help with healing. You can get the thermazene here:
http://www.amazon.com/Thermazene-Silver-Sulfadiazine-Cream-grams/dp/B0008KLQNM
What was the initial cause of the tail problem? A bite or retained shed?
Have you checked for other vets that could do it cheaper? I hate to even suggest it, but a regular vet could most likely perform a simple amputation since it is just the last couple of inches, but if that dead tissue does not come off & there is infection in the tail, it will travel & there is nothing you can do to stop it once it starts traveling except just cut the infected area out.
I cannot approve you to try to amputate at home, that is way too risky. The only thing that I can recommend you to do right now without going to the vet is to get a magic marker (non toxic, non permanent) & draw a line on the underneath side of his tail on the soft tissue, to mark slightly above where the discolored area on the tail is. This will help you keep track of the affected area on his tail as to whether or not it is traveling or not.
I will send you a PM regarding medications, as well. This is absolutely imperative that you get this taken care of. Infections that spread can quickly kill your dragon.
Tracie