Firstly, I get whet you mean about a "failed" life compared to the rest of the population but, you're not the rest of the population, so you're comparing apples with oranges. You have ASD and only a small percentage of those with diagnosed ASD are in work. Your job may be dead end, but you're maintaining it. Compared to all the others with diagnosed ASD, that means you're doing amazingly. You're also maintaining an independent life, in the flat share. Lots with ASD can't do that either, not without someone else running the show.
The way forward is to take some practical measures and MH measures.
The thing to give up on is the toxic family. They know you have ASD? If so, you might like to tell them what I posted above about how well you're actually doing. If they're still rude enough to comment negatively, or if they don't know about the ASD and you'd rather keep it that way, just tell them to mind their own damn business. You don't owe rude people politeness and rude they definitely are. Allow yourself to grieve that you didn't have a better family. See less of them. Make more of your friendship circle, invest in them instead of family.
Once you're away from that toxicity, work on your self esteem. They've dragged it down all your life. Basically it means doing things you're good at so you can get a boost from achieving something. It doesn't matter what it is. Also if you can, push yourself out of your comfort zone to achieve new things or at least try to, whether that's hobbies, meeting people, setting yourself a personal fitness goal or whatever. Set small manageable tasks, push yourself to achieve them and then, this is important, celebrate those achievements as they occur. Do this and you'll start to feel more positively about life and yourself.
Jobwise, I think it's time to accept what is and stop lining yourself up to be rejected on a regular basis, because that won't be doing your self-esteem any good either. Ok, so you have a dead end job, but can you build on that at all? Can you one day become the supervisor or manager? Can you apply for jobs within the same company, eg that would move you from the shop floor to the offices? If not within this current company, what about within new ones who do the same job as you do now?
Also look at the positives. Does this job suit you and your skills and personality? Are the bosses happy with you? Can you cope with the job without it keep making you ill? Do you like your colleagues? If so, there's a lot to be said for all that, when it comes to life and happiness. Appreciate what you have and focus less on what you don't have.
If there are huge negatives, like if you have a zero hour contract and feel job insecurity, get another job doing the same thing but in a company that will give you a permanent contract with guaranteed hours, small improvement to life in this way removes stresses and makes things better overall. It's an achievable goal that improves things, instead of trying to get a totally different job that just isn't happening and knocks you down.
Get yourself on the list for social housing right away. It may take decades for you to get a place, but one day your turn will come and you'll have a flat of your own that you can afford on a low wage and the chance to put down roots and turn it into a home. Remember to update your records if you ever get evicted.
Not everyone who wants a partner gets one and that's sad, all you can do is get on with your life, don't wallow in self pity (because that's not an attractive trait) and keep an open mind that you may meet someone one day who is the right person for you. The key is to be in situations where you meet people (unless you want to do online dating, but personally I think that sounds soul destroying and I think you first need robust self esteem to cope with it, although some do find success that way) because you're not going to meet anyone sat home alone. So you need sociable pastimes to keep the possibility of meeting someone alive.
Focus on you and making your life the best it can be so it's not as disappointing if it never happens. Nobody is going to "save" you and it often leads to an unhealthy relationship dynamic if they try to, we each have to "save" ourselves by creating our own best lives, where having a partner is the cherry on top of the cake, but the cake is still good by itself even without the cherry. That's how to be content in life and not get stuck in unhealthy relationships with people who are all wrong for you, out of fear of being alone.
You're obviously a proactive person and that's good. Your original plan wasn't a bad one, it just hasn't worked out. I just think you're focusing your energies in the wrong places at this time in your life and would benefit from a shift in focus.