We all feel down in the dumps sometimes. That doesn't make those feelings any less valid

You're doing much better than me. I waited 17 years before going to see a therapist last year. Sorry to hear about the support group situation. At least you're here on Susans!
I see a voice coach every week - 2 weeks who gives me various exercises to do. Others on here could probably provide do it yourself programs and advice. My Adams Apple and some facial features are quite masculine (someday soon, I'll actually post a pic here with my face showing), so I have started looking into providers for facial feminization surgery, which can make some of that better. I'll always be 6'2" though, which is my big hangup (but so are Maria Sharapova, Karlie Kloss, and Gwendoline Christie give or take an inch....).
My original thought on passing was that if I didn't, I would just deal with being male, as a big part of my dysphoria was knowing there was something I could at least try and do about it. I would be disappointed about that, but I try not to let things I can't control bother me too much (easier written than done sometimes). I'm at a point now where if I don't pass, I'll probably stay as I am, and would take comfort in knowing I did all I could. While that isn't as nice as passing as a woman, it feels a lot better to me than living a lie as a man. Part of why I waited so long to seriously consider transition is I found it very overwhelming when I first researched it (I was around your age then). It can feel like a daunting process.
I guess where I'm trying to go with all of this is that we can't predict the future (in which we know we're unhappy) and the only way to get to a place where we might be happier is to go through this process. Once you have the actual results of it, you can then figure out what to do. And, you might be underestimating your odds of passing, as at your age you have a better shot of it than folks who are older!