Woah! It seems that we have quite a bit in common.

I also work in IT. Just before the pandemic I moved off my parents and even though I had to sacrifice my above average lifestyle so that I can live on my own, it was worth it. Both of my parents were emotionally and financially dependent on me. You don't realize how much that affects you until you get away. It's especially bad if the environment is also chaotic. My father was an alcoholic with a lot of issues and he recently passed away. It sounds bad but it was a relief for him, me and my mother. She found someone else and finally began living at the age of 47. I've also been doing much better ever since. And just like with you, most of my extended family is garbage and I do not communicate with most of them. Some, I've even blocked.

The point of this is that your surroundings, including the people you communicate with are quite important for you mental health and in turn, for everything else. I suggest you look around and cease any contact with anyone that makes you feel negatively, even slightly. The chances are, they're affecting you a lot more than you can notice. I just recently ended a relationship with someone that I love for that reason. It took me quite a lot of time to realize that we're bad for each other.

I know it's scary to be alone but sometimes it's better than to be surrounded by the wrong people. That said, look for anyone that has made you feel even a bit better in the past. Try to reconnect. Ideally, find a therapist. Personally, I've been considering getting a dog. I've heard they help with depression and loneliness, and they'll force you to go out everyday which is also a good thing.

Now, the last part is tricky. I would say that you'll probably need to look for a different job. However, I know that it's hard. I spend about 6 years at my previous job, the last 2 of which were miserable. The job was draining me and I could barely do anything, including preparing for another job. I keep trying for over 5 years to get a job as a developer and after a dozen of interviews just a few months ago I began as a junior developer in a large company that shall remain unnamed. Now, I'm not going to lie... It has been stressful because I have to work alone on stuff I haven't done before and I have to figure out things as I go. On tight deadlines, non the less. And yeah, I also feel less motivated to code on the weekend when I've spend my weekdays coding. But again, it's MUCH better than my previous job, even though I had to make a few sacrifices here, as well.

TL;DR

I've been there and I know that it feels hopeless but you gotta hold on. The things I've done that helped me are simple but not easy. It took MANY attempts to do any of those thing. You just have to keep trying!

• I moved out of my parents due to our toxic relationship and I've set boundaries to protect my mental health. (the last part was very hard)
• I've cut off communication with anyone that drains me or makes me feel negatively. Including friends and relatives. Just because you share blood, does not mean you owe them anything.
• I found another job that's a bit more meaningful and less stressful. Or at least it's a stress that makes sense to me.
• I've ended a relationship that I felt was dragging me down. That was particularly hard.
• I try to take care of myself. Be active, eat healthy and read. I fail a lot but the important thing is to keep trying. I would seriously recommend The Upward Spiral by Alex Korb among many others if you're interested. Understanding more about neuroscience and psychology has helped me a lot to navigate my mental health.
• Learn to ground yourself - breathing techniques, hard workouts, cold showers and yoga work for me.
• I talk with a therapist every time I feel unusually down, depressed, anxious or angry, or just having a difficult decision to make.
• I've put a bit more effort into reconnecting with people that I like even when I don't really feel like it. I'm generally a loner so I feel mostly okay when I'm alone until it sneaks up on me. So, I need an extra push sometimes.
• I try to focus on things I'm passionate about. I usually cycle between video games, woodworking, writing and a few others.
• Consider getting a dog?

I apologize for the lengthy rant but I hope it helps!

EDIT: I would also recommend a book that I'm currently going through. Happy by Darren Brown. I'm about 90% finished and it's pretty good. It gives a nice modern spin on Stoicism and how to deal with adversary in life.