Gosh, that sounds hard letitgo. Worry is the hardest thing about being a parent. It is for me, anyway.
Do you mean you tried coming off Lexapro too? Cos it's pretty cool being on that stuff (SSRIs) over the long term, and can be quite helpful. Xanax is a bit different. It's easy to get into a situation where all it is achieving is staving off withdrawals and not much else. Not giving advice; these are just well known facts, and you probably know them already! Have you tried other things besides xanax for anxiety?
I'm pretty much right these days re anxiety but I know what it's like - not pleasant. Great you got this recent situation sorted, and good for you planning to let your psych know you are displeased. It will be interesting to see how he responds. Like you say, it might be better to go elsewhere...time will tell.