Many years ago I was in your position. That was when I was still driving and at the point of hardly being able to get to work for the anxiety/agoraphobia. Once at work, I would be worrying ALL day long as to how was I going to get back home. I lived maybe only 15 minutes from work.
In those days, early 1980's, there wasn't much in the way of meds or even medical understanding/counselling.
I do understand about taking the extra Xanax to get into a 'state of mind and body' whereby you can even get into a car. There was a time when I had to lay in the back seat with my eyes shut and the music blaring on the radio to block the thought I was in a car. I had Valium at the time and would take enough to make me 'very' relaxed.
If you cannot cope with driving, I certainly wouldn't be thinking about a long trip driving. Consider another doctor, consider any resource in a positive direction to get you living with this. I say this because, I am fairly convinced that without meds, no one ever gets completely over agoraphobia. It's always in the back of your mind, like waiting for that other shoe to drop.
Speaking from a long term sufferer, I wish the options had been available to me that are to you because I gave up driving 13 years ago. It became just too much of a daily struggle and I could find no help. Agoraphobia can take over your life if you don't get on it...the learned behavior becomes so ingrained in your brain that it becomes impossible to improve.
I don't want to scare you in any way. Just want you to realize how cunning and manipulative this disorder can be and ultimately devastating in a very permanent way....please keep looking for options and my very best to you.....