I think it all revolves around your alcohol abuse. Starting the day with wodka is never a good idea. And you being 18 at the time does not make it better.
Realism should tell you that not your person made her do this but your addiction/alcohol abuse and your depression.
You probably said some things due to that combination which were awkward or maybe even scary. Or, which is also a thing, your "state" made her anxious and a little bit scared. Quite possibly both. You said strange things and she thought you scarey looking.
So far so good. I can rationalise that all since im no part of it all.
Now comes the assholes part: your school, everyone there , were assholes for making you sign that. It was stupid, it was kicking someone when their down. You needed help, not restrictions.
You needed a talk, no "contract". Like: Yo, this girl is a little bit scared of you and prefers not to talk to you anymore. She is afraid to tell you this in person so I'm doing my job as a school official. So back off from her and frankly: you need help. Lets talk about that. Etc.
That's what shouldve happened.
That would be brutal but honest and such is life.
This? This was the easy way out.
Continue existing? Of course. Living is learning and you learned from this since you've sobered up. You're great for accomplishing that. A lot of people can't do that!
Healthy relationship: start with "just" relationships. Find out what interest you and get together with other like minded people. Just be you but always be clean and neat. People tend to stick with the first impression they get of someone. Being, what's the English word, groomed? Is a big part of that. Healthy will come, just you wait. :)
No longer a threat: here you go, this is probably what freaked her out. Be honest to yourself. Don't sugarcoat it. You can't heal if you're not real (to yourself).
How, why: she was scared, plain and simple. She didn't dare to tell you no because she was afraid of what might happen. Account it to "shit happens", learn from it and move on. Moving on from a crush is hard, yes. But you must. It's been 6 years. A lot has happened in that time, no?
Hate yourself : wtf dude? Here you are, changing, sober , in therapy... You matter! You deserve to exist!! There is so much more to experience, some good, some bad. Both are needed for a balanced life and worldview.
Some days will be bad, some days will be good. Most days are in between :). Every experience is worthwhile. Every moment only happens once. Be there to experience it, however banal it is.
Life is such a short stint in eternity. It's a strange, rare gift in this universe and because of that worthy of experiencing. Because there comes a moment you won't.
Its like they say in GoT: what do we say to the god of death? not today.