I live in a dangerous transphobic place (in the southern U.S.) and I socially transitioned months before starting HRT later in life (I'm only 7 months into medical transition, and almost a year since socially transitioning). You definitely don't have to take HRT to transition socially, some people never take HRT and only socially transition (I would work with your therapist on why you feel you don't deserve to socially transition). When I socially transitioned I did not remotely pass in the way I looked or the way I sounded, and I still don't pass most of the time. (I think sometimes I pass now when just walking around in public, but even at a distance lots of people can tell I'm trans. I think I just went from "man in a dress" to "that person looks trans / gender-ambiguous".)

All the anxiety you talked about was present for me, and you are right, it is crippling. I remember at one point googling like "how to deal with feeling so vulnerable and scared" and things like that. It was truly overwhelming. I thought I was going to be assaulted the first time I wore a dress out of my house (which was mostly in a car driving and then in the waiting room at therapy to talk about my gender dysphoria^1^). But what I found was that almost nobody cared. The worst of it was just intense stares in places like grocery stores or restaurants, almost always from hyper-masculine looking men. It is rude, but it's not the impending death my anxiety tells me it is. The reality of being seen as an "abomination," as you call it, in public is radically different than how you think it will be, and tbh most people just don't care if you are trans.

What I can say is that with exposure to situations like that, over time the anxiety lessens significantly. I felt panicky the first time I started to change my voice at work. I felt panicky the first time I wore a dress in public. I felt panicky the first time I came out to people at work or in my family, etc. But now, six months later, I get mild to moderate almost performance anxiety before speaking at work. It is mostly in the anticipation where the anxiety presents still, the waiting when I know I need to speak and the feeling that I won't be able to produce a natural sounding feminine voice. You just get used to it, you get used to looking trans and not passing and sometimes people looking at you. (You probably won't have nearly as much of a hard time as me, being so much younger, especially if you start HRT soon.)

What helped me was to recognize that because I couldn't perfectly pass, I should relax while I'm in-between and still early in transitioning, so I can actually more effectively train my voice and feel comfortable in social situations. Perfectionism, the demand that you never slip and let anyone know you are trans, is unrealistic and counter-productive to transition. The tension and anxiety caused by that perfectionism get in the way of actually using a passing voice, for example. I get why we all feel that perfectionism, but at least for me passing is so far away that it was helpful to let that go as a strict requirement. Instead it's a goal that I intend to orient towards, but which I recognize I will continue to fail at. Focusing on the failure doesn't help me reach the goal, so instead I focus on what I can do to help get closer to the goal without getting so attached to the outcome that I undermine progress.

It's hard to give advice, I don't know you or your situation. I think if I hadn't socially transitioned when the iron was hot (i.e. right after my egg-cracking), I am sure I would be having a lot of difficulty deciding to socially transition later. So I guess my tip to deal with the anxiety is to "just do it" and keep doing it and know it gets better. It is important to stay within "threshold" (i.e. not push yourself so much that you completely break down), but you might be able to handle more than the anxiety makes you think you can handle.

A part of my envies you, transitioning at 17 would have been much more ideal for me in terms of being able to pass. A lot of masculine features didn't appear until my 20s, and it kills me that I didn't transition younger. I think about the whole life I missed, not just as a woman but due to the depression and problems the testosterone caused me. Remember that you are doing something really kind to yourself, it is a gift to your future self. And remember you are not alone - lots of us are going through the same thing you are.

Oh, and I guess that does bring me to a certain point: starting estrogen can be destabilizing in some ways, but for me it massively helped my mental health, especially after a couple months of injections. I didn't find bicalutamide (an anti-androgen) helpful for my mental health symptoms, and spironolactone has lots of reported negative side effects including creating mood issues so I refused to take it. I use estrogen monotherapy as my "anti-androgen", i.e. sufficiently high levels of estrogen will block testosterone from being produced by the body. Estrogen is pretty safe when injected (oral & sublingual routes are less safe, though maybe most people are fine taking them; I just don't think oral would be safe or reasonable for monotherapy, it's too much).

You may or may not be like me, estrogen may or may not help your mental health. But before HRT I had regular horrific nightmares, anxiety, depression, constant passive suicidal ideation which at times became more acute and became intrusive active suicidal ideation, and a general unhappiness / grumpiness all the time. Estrogen literally reversed all of it. Estrogen most immediately solved my suicidal ideation, my unhappiness, and my depression - within a week or two of injecting, my motivation and energy were unusually high and I was getting things done that I had been putting off for literally years. I felt naturally happy for the first time since I was a child, and I realized I felt happy to be alive and no longer felt passively suicidal which hadn't been true since I started puberty. The anxiety continued to be a problem for me but after a few months even that subsided dramatically. I think it takes a while for the body to adjust to new sex hormones, or at least it did for me. I still think it is adjusting and I have off-days sometimes, so it is not a silver bullet - it just made a big difference for me, made me a much more functioning person.

Not all trans people experience this, and estrogen doesn't fix all mental health issues. It just really helped mine, and who knows - hopefully it helps you too.

^1^ By the way, I found the therapist by searching online for therapists that are trans-friendly or deal with gender issues, I would advise the same since you may need the therapist to write letters for you if you elect for surgery (which is something I didn't think I wanted when I started transition, but which changed pretty dramatically over the months, so keep your options open), and they may need to refer you if you decide to get an endo once you are 18 and no longer subject to your parents. I also recommend looking for a therapist with a PhD in psychology in particular, not all therapists are equal. Also, having a therapist that isn't trans-friendly just seems like a bad idea. Transition will be a big part of your life and a therapist that isn't accepting is not going to be a good therapist for you. At the very least having the conversation early about what they know about trans people and whether they are supportive or not will help you evaluate whether it is a good fit. You should also know, in places like Missouri, an autism diagnosis is used to deny HRT, so consider the cost / benefits of getting a formal autism diagnosis depending on where you live and what kind of legislation may be enacted. Trans panic is in full swing, so I just encourage being strategic (which is contextual, again - I don't know your situation).

I wish you well - good luck in your transition!