I understand how frustrating that must be. It sucks to have people tell you all of your life that you can't do certain things because of your intelligence and then have someone tell you it's "not real".
I think most people who say this (including the person you're replying to) are trying to reassure you, not dismiss you. The origins of IQ are arguably racist/classist and the science behind it is disputed by many. I was told all my life that i had an above average IQ, but i never understood why. I didn't feel smarter than my classmates and I did poorly in school. I later learned that I did well on the IQ test because of my economic background and the resources that I had available to me from a young age.
Intelligence is such a broad concept that we frankly don't fully understand yet. So the fact that we measure peoples intelligence and worth over a number is bullshit and dystopian. This is where the split in your experience comes from. You feel the effects of a low IQ because society values it too much. But most people know it's a metric that's used as a cudgel against others.
In other words, I very much believe that you are treated differently and have fewer opportunities as a result of your IQ, but that's an indictment of our society; not you. On top of it all, it sounds like you didn't have the support network that other people have. Verbal and physical abuse from the people who should be our guardians and champions (your father) will stomp the spirit out of anyone.
I know it might not be comforting, but I read your post and you didn't seem unintelligent to me. Sure, your sentence structure might be different than mine, but you seem like a thoughtful and connected person. What I'm missing, most likely, is the effort, time and energy that it may have taken you to write your original post, which i dont want to discount. But you're able to get your thoughts and feelings across just fine, at least in the form of writing.
Alright, enough with the pep-talk. Do you have any interests or things you like to spend time with? Video games? Animals? Exercise? Drawing? Writing? Makeup? Anime? Cooking? It doesn't matter if you think you're bad at them -- I'd recommend pursuing those interests. Sometimes volunteer work opens up opportunities that you haven't considered. It can also help you create that social safety net that I was talking about earlier.
I would try to get a job that gets you by (I know, easier said than done). Something like janitor work, fast food, retail, or hotel service. It doesn't have to be permanent, but just something to keep a cashflow while you give yourself time and room to grow. I'm not sure where your located, but I would check for non-profits or local orgs that offer assistance to folks.
Don't let our psychotic and unhealthy society dictate your worth. You are a human being who has thoughts and feelings. Your ability to hold a job or quuckly solve a problem is relatively superficial.
My 99 honda civic had nearly 250,000 miles on it the day that it was stolen. When it was found, the thieves had gutted the dashboard of electronics and had removed wheels and other parts. When it was discovered by the police, they towed it to the city in-pound lot and failed to contact me for a couple days because the license plate had been painted over for some reason.
Unfortunately the lot and towing fees ended up being more than what I paid for the car. I wasnt very well off at the time, so I surrendered it to the city. I assumed it would be scrapped for parts.
6 months later it was served to me in ad for Facebook Marketplace. Some guy had fixed it up and had been driving it regularly for months with no issue.
I still wish that I had bought it from him. I fuckin loved that car. I used it to deliver pizzas for 2 years, so i wasnt even that easy on it. I never had a major engine or transmission issue with it and the minor issues that I had were easy for me to fix myself. I bet it's still running out there somewhere.