I'm not really sure what your question is, but I'll give my best shot at assessing your situation. I'll be honest there are a bunch of red flags here.

First off, you should definitely save up before you head out. Before even thinking about going, I'd recommend that you at least have ways to feed yourself and put a roof over your head.

About needing a special diet: is it bad enough that you couldn't eat stuff out of dumpsters / food that people give you? I think adaptability is a good quality to have wherever you are. If your diet needs to be watched carefully it might not be reasonable to hit the road. Assess if you can still moderate your diet while wandering.

About have social anxiety / avoidant personality: The only way to improve these is to get out and meet people and talk to them and be forced into a situation where you have to socialize. I'm still a huge introvert, but most of my social anxiety has disappeared. It used to be bad enough where I couldn't talk to anyone on the phone or talk to people I didn't know. Work on talking to people and moving past these problems.

About the addiction problems: End these now, in any way possible. This is very important and probably way more important than any of these other things I mentioned. Addictions are only a financial drain and can make existing mental and physical problems issues worse. Not a good combo when traveling. Try to get sober.

Oh, also: try to build up skills as well. Go to your library or read some material online about relevant skills: gardening / permaculture, small-scale construction, writing, crafts, general coding knowledge... that sort of thing.

So, in summary: get clean, learn skills, save as much money as possible and work on anxiety issues. Hope this helped