I've been reviewing your notes, and I sympathize with your situation. I can see that it is deeply frustrating. I'm the mother of a 13 year-old daughter, and I sometimes think they exist to be contrary! There are certainly some legal things going on with your story, and as a Parenting expert I don't have the expertise to address those...they will resolve themselves naturally as your ex and you work things out custodially in court.
As far as your questions concerning your relationship with your daughter--I feel your frustration! A great deal of what you are going through is the age, compounded by the sensitive nature of the situation. It sounds as though your ex is doing what you have sense enough not to do--he is manipulating the emotions of a child and using them for his own gain. Please continue to be the better parent. Children simply do not have the emotional maturity to handle the tough issues of why adults do the things they do (such as abuse drugs and abandon them for a time, for example). It's not fair to burden them with information such as that. You are doing absolutely the right thing--although painful and frustrating for yourself!--when you tell your daughter that you are acting in her best interest when you deny your ex primary custody.
It is okay, as a parent, to sometimes say "because I know what is best for you," and leave it at that. There may be a space of resentment, but that son or daughter will sooner or later come to realize that you make the decisions that you do because you love them, and wish to protect them.
All that said: if I understand your communication correctly, your daughter lived with your ex for two years while you were getting yourself together after a bout of depression, until this summer? It is VERY natural that she would feel the resentment and hesitation that she does at the idea of moving across the country after such a long absence. She is probably wondering if this uprooting is something she is going to have to deal with on a semi-regular basis. My best advice to you is to give this some time. Compromise, if at all possible. Reassure her that visitation is an option, and show her how it would be possible.
I hope this has been helpful to you. I know this is a tough situation, and there are simply no easy answers. Best of luck,