Hello, so I'm not autistic as far as I'm aware, but I do have ADHD-C and have also greatly struggled with anxiety throughout my life. I hope my experience and knowledge can be of some use to you.
To start off, man, hard relate on both those fears. I mean different mechanism for me in terms of fear of trying new things since it's more of a "how much time and money am I gonna sink into this obsessively only to completely lose interest in an indeterminate amount of time?". And to your second point, yeah, the world isn't built for those of us who aren't nt. I could go on and on about many anxieties I continue to struggle with to this day, including worry about never truly gaining mastery over myself, losing access to healthcare and/or medication my wife and I need, and external events of climate change, political turmoil, anti-intellectualism, misinformation campaigns, and academics seeming to be losing their fucking minds when it comes to anything philosophy related. I just want to let you know that you're not alone.
As for how I've dealt with this in my life, it's primarily come down to Stoic philosophy. Especially when it comes to the anxiety, it's usually about the framing of how I think about something--much like how modern therapy looks for underlying beliefs and/or experiences that may be a root cause. Someone cuts me off while I'm driving, so I become angry, but it isn't the other driver that has made me angry, it's my opinion on the matter. While it's true that they shouldn't do such things because it's unsafe and can cause harm, it's possible that they didn't do that on purpose and/or out of malice. Even if they did, what would my anger truly accomplish other than increasing my potential to escalate the situation? In fact, if they truly are a 'dumbass' or 'idiot', why would I become angry with them when they act according to their nature? Ultimately, I'm not in control of that person, so why react in emotional futility? I'm in control of me and how I treat others with respect, kindness, and charity. I just give them some extra space for everyone's safety and move on. It's about what I can and cannot control. I cannot control these externalities of reality. It's reality, why not just neutrally accept it as such? I must keep in mind that I always have the option of not having an opinion.
I've always struggled with anxiety in my relationships and my marriage is no exception. I fucking love my wife. She my best friend, the best lover I've ever had, and my whole world. But I don't own her. She isn't mine to keep forever. As the bittersweet saying goes; this too shall pass. She could leave me, she could suddenly and rapidly decline in health, she could die today or in 3,000 years, we could be married for just one more year or maybe 100 more years, who knows? What I do know and can do now is love and appreciate her now, because, well, she is what matters to me and someday she will no longer be in my life. I must admit that despite my many years of therapy, bettering myself, and practicing Stoic philosophy, I'm certain I couldn't handle suddenly losing my wife right now. I don't mean that in the sense that I ought to be able to emotionally shrug it off, because that's insane, unrealistic, and counter to Stoic philosophy, but rather in the sense that I would lose rationality. While I recognize this is a problem, I have found that it's something that is too insurmountable for me to master on my own. So yeah, I still need therapy and I must accept that this is where I am in my efforts to master myself.
The important techniques I've learned that have worked for me that come from Stoic philosophy is daily self-reflection, mindfulness, constant reminders of what I do/do not control, reminders that I will inevitably run into daily troubles, and 'amor fati'(or 'love your fate', that is: to not only accept your life as it is, but to love and appreciate it while you have what you have). Constant self-reflection is crucial because no one truly "controls" how they immediately react to things, as it's the beliefs that will dictate the outcome of your reaction. I became more calm as a driver because of my end-of-day self-reflections in examining why I reacted the ways I did and honestly reasoning with myself about it, which led to me catching myself in those reactions more and more until the unreasonable behavior waned into the past. It's the same with my anxieties, although much more of a game of whack-a-mole and work in progress. But boy have those moles dramatically decreased their frequency in popping up and boy have I regained so much of my life by no longer ceding control of myself to them.
If you want further resources, I strongly recommend reading Meditations by Marcus Aurelius. I can also recommend videos from The Daily Stoic with the asterisk that he can get a little... 'markety' every now and again. As I like to say; eat the meat and throw out the bones. And, of course, I always recommend finding a good therapist that you click with as this stuff is their specialty. I mean, obviously, sure, but I think it's worth mentioning that much of modern therapy finds it's roots in Stoic Philosophy. Anyway, I hope my wall of text is of some use to you or anyone else who took the time to read. I'm open to questions, comments, and any accusations... or just a shrug. It's up to you, afterall, I'm not in control of you.😘
TL;DR: Can relate, although not autistic. You're not alone, your feelings are valid, I recommend Stoic philosophy, I give examples of how it helped me, read Meditations, and I feel gross for using an emoji, but like ¯_(ツ)_/¯