Autism

Warning: Hot take: the longer I’m a parent, the more I feel that we shouldn’t be able to have children

First of all: you personally experiencing personal difficulties doesn't entitle you to tell others they "shouldn't be able to have children". I understand that it comes from what's possibly a deep personal frustration, but it's nonetheless disgusting.

Now that that's out of the way. You need to calm down. The first reason you shouldn't be beating yourself for not living up to your expectations of what a parent should be is that you've got to take a look at the general state of parenting. The vast majority of parents are pretty much shit at it, only got children because they wanted to go in with the vibes, and will very rarely question themselves for doing things far wrong, and want their children to be small copies of themselves. My own parents weren't great parents! One of them was a disgusting imitation of a human being who relished on provoking suffering to those around him, and the other had far too many issues of her own to take a clear stance on things when they needed to be done, but at least she was loving and ultimately was there to support me when I needed it. I'm not going to reproach any parent for not being able to provide anything more than what my mother could, because it's clear that far, far too many are well below that minimum.

Moving on.

2 year old son (...) Today I had an appointment with my son’s speech therapist, because he’s still not talking more than a couple words. The appointment is unstructured play and interaction including mimicking him, waiting for his cues, etc. The problem is, I can’t pick up on communication cues or read what to do next. I can’t communicate with him like a normal parent and I feel like I’m holding him back.

I didn't speak until I was 3 years old. Then I was the very first one kid in my class to learn how to read and write. Different people have different learning curves, and autistic people tend to have very different curves compared to the average person.

My actual specific advice here: make sure your kid doesn't get overwhelmed, much less in therapy. I have the growing suspicion that a lot of autistic kids don't learn too well to communicate verbally because they're disincentivized from doing so, both by their own senses and their environment. As any person should be able to understand, personal difficulty and lack of motivation to learn a skill are going to get anyone to hide their head underground like an ostritch and refuse to learn, and by actively frustrating autistic kids, these lose motivation more than anything else. Your most important goal here is to make him want to communicate with you, but not out of need, but because interacting with you will make him feel well.

I am excluded by other parents because I’m weird or different, and they keep their kids away from us when playing at the park. I want him to be able to socialize and have friends and his autistic monster father gets in the way.

This is mostly a "they" problem. It's not your fault that other people are closeminded assholes who want to exclude you for not being typical enough. Do not get discouraged, keep being a father in public places and you'll end up coming across good parents that you can reach out to.

How am I supposed to help when he gets to school? I have trouble with numbers and can’t do math😭😭

Are you going to beat yourself because you aren't good at math??? How many parents do you think are good at math!?!?!?

I'm going to be blunt and honest. From my extremely limited perspective of knowing you as a person who has written a few paragraphs online, I think you're mostly suffering from low self esteem, stress and anxiety because a lot of different things in your life aren't going like you think they should, and this makes you being extremely suspicious that you being a parent is yet another thing that will fail. If I'm correct in my premise, you have to know that your conclusion is very faulty. Shit, even. You clearly care a lot for your son. Make sure you look after yourself so that you can look after him, and I'm sure you'll do a decent job.

Remember that parenting is a very time-heavy endeavor, that pretending to have two people only doing the whole parenting thing themselves is a modern, non-sensical ideal, and reach out to your outer family when you need to, that you have to prioritize your son's happiness over him being "normal", that neither the extremes of throwing your kid into the pool nor never caring about their development are good, and things will turn out as best as they'll be able to, which are probably better than you currently thing. Oh, and look out for sensory overstimulation. That fucks up a lot of autistic children and no one knows any better because they don't know how to communicate it.