I too was a big fan of Xanax. I got the best results when I first started taking it. That's only natural as benzos generally work the best on "naive users" (as psychiatrists like to say).
The fact that I built up tolerance to them made me take more and more and ditto, I was addicted before I even knew it. It's no secret to doctors that Xanax is one of the most addictive medications out there.
I took so many Xanax pills that I messed up my stomach/ GI tract. After a while of taking large quantities of Xanax, I started to feel like the taste in my mouth was changing. Everything tasted sour. It's because of the Xanax. If you put a 0.5 mg (those are the ones that I would take) Xanax pill in your mouth you will see that it tastes horribly sour. So, you can only imagine what a high quantity of Xanax will do to your stomach. Anyway, what made the pills' impact on my stomach even worse is the fact that I wouldn't take each pill with a full glass of water. People tend to ignore this doctor recommendation. I surely regret that I did....
For me, quitting the pills wasn't so hard because my body would basically start to reject them. It made my stomach feel really bad so I just could not take any more of those pills. I can't even take ONE pill anymore. Now, I pretty much get the same reaction when I take any Benzo, not just Xanax. So, pretty much, in a sense, I was lucky because my body stopped the addiction for me.
I ended up taking a much higher quantity of Xanax than was prescribed but NEVER got close to what you are taking. I think you are able to take that many because you have a very high natural tolerance to Xanax or Benzos, in general. Xanax is not a brutal mind-altering drug and that is why tolerance to Xanax builds up very quickly. That's the reason doctors generally don't prescribe it for more than 2 months.
On another note, towards the end of my Xanax taking days, I would start to get really strong paradoxical effects. Instead of relaxing me, the pills sometimes caused severe agitation. Not very fun...
I don't know what other drug to recommend, but since you said that you have already tried everything, my recommendation would not be needed. Right now I am going through a period when I am not taking anything for the anxiety/itching/burning but I do miss those pills sometimes... :)
Anyway, I basically wrote this to alert you of my GI issues that were caused by Xanax because they are not very pleasant. Not at all....
Take care and be well!