I have a lot more thoughts on this, which will probably not be that well organized.
On finding a therapist: unfortunately, I haven't had a lot of luck with this. Most therapists aren't very good, and the more statistically unusual you are (and the more ways you are statistically unusual), the less likely you will be to find a therapist who is culturally competent, so to speak, to treat you.
You're going to have to kiss a lot of frogs, unfortunately. Maybe the best you can find will be a frog with a crown who can sort of look like a prince if you squint at him right. I find it useful to keep in mind that a therapist is someone you're hiring as a consultant to help you figure out how to run your brain better, and their job is to eventually make themselves obsolete; the responsibility ultimately rests with you, and the more you learn and figure out on your own about your psychology, the easier the process will be.
(Ahem, unless your therapist's ego is threatened by you learning about their field. Psychology/psychotherapy is one of my passions, and I've read a lot more books and articles about it than most therapists have. Most of them do not like that.)
On "coming in 20000th place": if you're coming in 20000th place in the entire world, that's nothing to be ashamed of. Coming from the assumption that you can rank people linearly, the chance is 1 out of 7 billion+ that you're the best in the world at whatever you strive to do. Not very good odds.
(And I think linear ranking is an oversimplification. Was Einstein the greatest physicist who ever lived? According to what scale? Who was the greatest artist that ever lived - is that even a meaningful question? Everyone is unique, and has their own unique contribution to make that no one else can make.)
On challenge in classwork: unfortunately, as you've found, classwork likely isn't ever going to fall in your zone of proximal development and stay that way. That doesn't mean it's worthless; it just means you need to have realistic expectations of what it can be for you. Classwork is there to get you to master a set of skills or concepts; you will pretty much always be faster at that than the pace of the course.
The value I think classwork has is as a social pressure to do exercises on material instead of putting it off, and as an exposure to the larger conversation about and terminology of a field, and as a way to get to know people who are interested in the field. Some classes also have assignments whose ceiling you can raise yourself (unfortunately, math problem sets are not usually in that category). If you approach a class as like... a garment that comes out of the box in a standardized shape and size, but that you can tailor, dye, embroider, etc., to get as much enjoyment out of it as possible, that's a much more realistic attitude to have than expecting that the class will be automatically tailored to you. It won't.
On having to jump through a lot of meaningless hoops: yeah, that's how the world is. I think most autistic people resent this on some level for their entire lives, but eventually learn to come to terms with it. I think that's one of the developmental tasks of autistic young adulthood.
I think some perspective-taking helps with this. You want to make a contribution - great! But every single person who has been recognized as making a contribution, whose work didn't end up moldering in an attic unappreciated, was able to communicate that contribution to others who did not think exactly like them (or else their contribution was discovered by the wider community after their death and they were only appreciated posthumously, which I don't think is what you want). It's like how Saussure said that no one person can change a language singlehandedly - because for a change to be part of the language as spoken by a community, it has to be adopted by the community.
Learning to sell your contributions is a skillset you're going to need to learn. Even if you get a tenure-track job, you're going to have to apply for funding, write papers that reviewers will want to publish, and convince your peers of the value of your work. Not to mention teaching.
Finally, the question that's been weighing on my mind above all others: where were your parents in all of this? Are they actually in your corner, or are they neglectful and apathetic, or overly pressuring, or opposed to your goals? Because I think that whether you take a gap year at home, or whether it's very important to try to push yourself out of the nest, depends on the answer to that question.
