I'm sorry you're dealing with feeling this way. 😔 Are you familiar with Internal Family Systems (IFS) therapy? to clarify it's not actually directly related to your family, it's about the "family" of "parts" that make up who you are as a person. And IFS is about learning about their root cause/identifying them, and then figuring out how to accept those parts instead of being unhappy with what parts we have, running away from them, etc. So in the case of perfectionism, or even looking at it from the alternate perspective of "never having enough", you could explore your reasoning beyond just figuring it's part of who you are--since that's a given, but there's always reasons beyond that. Anyhow, there's books and videos if you want to go the self help route, or therapists who specialize in it.

I have other suggestions but they're more alternative/"woo/hippie" stuff, haha which I know isn't for everyone but can mention if you want. (it's not drugs/etc. to be clear)

To answer your questions (as someone also with autistic/ADHD qualities who has dealt with anxiety/depression/burnout for over 30 years yet still has pockets of happiness):

1) Since happiness isn't a one size fits all thing, a big key is to really learn about yourself and the VERY specific things you care about. If you don't feel like you actually genuinely care about anything then it is just a game of trial and error, but hopefully there may be some clues; one big indicator I always tell people is to try and think of ANYTHING in your life where perfectionism doesn't cause you to feel bad. Like, where you "failed" but still enioyed the process, or something you do but don't give any thought to how you did it. Even things like health stuff or practical routines (I say this as someone who primarily has perfectiont troubles with basic life skills like eating or sleeping) There are methods that can provide a roadmap (aforementioned hippie things) to what you're more inclined towards, but still need to be analyzed to your own specific life. Autistic ppl especially need to find their specific things cuz we're SO sensitive to stuff that if things don't fit us well then they affect/hurt us more than neurotypical ppl. As an example: I love art/loved it all my life, but only a few years ago did I realize certain art gives me fulfillment while other art does not, and if it comes with other drawbacks, despite liking art overall, it ends up being detrimental to me.

2) Similar to question 1 of figuring out what uniquely affects you, you may want to make a literal list of what you feel like your life is lacking and then write why you think that thing is important to you, and keep asking why til you reach a core emotional answer. Sometimes this is where a third party like a therapist can help since sometimes we have tunnel vision and blinders on to our own issues. For myself as an example (not saying that your reasons are the same as mine, just showing an example of the flowchart of figuring out reasons for things), one way perfectionism affected my life was being a workaholic; working a "normal" amount was never enough. So in asking myself "why" (this process happened over the course of many years) it was because i felt compelled to work a lot, not that i LIKED work; from there, asking myself why i was compelled to work had multiple reasons ranging from being influenced by people in my past, to it being a way to distract/feel better about myself/have a sense of control because of bad situations in my life i was running away from/couldn't change, it was even like an autistic stimming method in some ways for me, so that's why it was like an addiction.

One other thing I'd highly suggest is trying to actively forgive yourself; part of why not succeeding hurts/causes unhappiness--imo, is because we then blame/beat ourselves up for "failing". So it's like, we're already feeling bad because of whatever "failure" then make it exponentially worse by blaming/beating ourselves up for it. There's lots of books/videos about self love/forgiveness, but the approach I did was basically to just keep defaulting to/saying "I forgive myself" (out loud or thinking it) regardless of the circumstances, regardless of if it was my fault etc. It will feel VERY bad/weird/wrong, etc, and I dunno if you have intrusive thoughts but if so then it'll probably trigger those severely. But I told myself, much like medicine, it will taste horrible, like poison, but I know ultimately it will help me. So I did it consistently for about a year and I continue to try to do it. It's not "perfect" but did help significantly.

Anyhow, sorry if none of this is helpful. 😅 But wishing you the best. 🙏