I'd honestly just find another psychiatrist, they're very hit or miss with benzos. The thing is that is never discussed, is that almost ALL the medications that are prescribed for the brain create dependence. It took a long time for my doctor (I also suffer from all of the same problems as you do) to realize that I wasn't some junkie, but a guy who just needed his meds. I can't imagine not having the klonopin (same basic thing), as I used to also get panic attacks where my chest would be sore for days afterwords from the heart pounding so hard, it sucks. The ptsd attacks (actually for me c-ptsd, as I suffered from long term childhood trauma - and don't even remember most of my years as a kid).
Once you do find a psychiatrist that's willing to help you, then it becomes a very rewording relationship, working to solve the problem correctly, and if benzos is what you need, then that's what you need. There are very very few meds out on the market that have proven themselves safe for long term use. I know I have mentioned this before, but my grandmother was on Valium for almost 40 years, and was well beyond sharp. She was a champion card player up till the year that she passed away, at the age of 98. SSRI's have only been around since the early 90's, and we don't even know what the long term effects of those drugs are. Antipsychotics... are dangerous, but sometimes a necessary evil.
For what ever it's worth, for the ptsd, minipress worked wonders for me, and isn't a totally commonplace med for that problem yet, but the response rates have been proven to be extremely good. Won't help with the panic though. Therapist, as much as I really hated the idea at first have done wonders for me, and now research is showing that meds alone aren't nearly as effective as they are in conjunction with talk therapy. Panic and ptsd are two proven problems that can be worked out with a bit of time, and really is well worth it... if insurance covers it that is... Also, if you have the occasional beer or drink, don't tell them cause it is automatically assumed that you'r an alcoholic due to the ptsd. If the doctor wants to try a different SSRI or SNRI that you haven't tried before, give it a go cause not taking their advise can be seen as wanting just one thing. You then ask you long does it take for the SSRI to work (it's 2 weeks), then ask for something in the meantime. If the SSRI doesn't work, then try a different one, but stay on the Xanax - or Klonopin if that's their choice drug. It stays in your system all the time around the clock, so you don't have to worry about taking your meds if you have an attack, and really, all benzos have the same basic action, it's just a matter of how long they last... for the most part at least.
Good luck, and hope that this is of some help to you!