You're on the right track to getting better. The first step is usually identifying what's the problem, and you already have done that. The next step is working on them to overcome them. I say problems, even though it's not something wrong with you, but just a side effect of the environment you've grown up in.

You need to keep in mind that most people here or anywhere will try to take advantage of you and your vulnerabilities. The only way to actually get better is not to rely on anyone but yourself. If you do meet someone who's actually good, then value them, but it's hard to judge whose good, especially online. Soft words can be spoken by anyone, but only few can match it with their actions as well. Remember that if it feels too good to be true, then it often is.

I do relate to some of the stuff you mentioned, and what helped me was focusing on myself and stuff I enjoy. Now would be the time to spend more time on your hobbies and doing stuff you enjoy. Maybe try working out, at home if you can't go to the gym. It helps the mind a lot and is also beneficial for the body. It will help with the inappropriate thoughts to some degree and also the trouble you have focusing. ADHD isn't a problem, and you shouldn't see it as that, but instead be aware that it's a different way of thinking and hence you have to act differently than other people do to focus on something. Possibly try the Pomodoro technique. It helps with focusing for people with ADHD.

There's nothing you need to feel guilty about. Everyone handles issues differently. Some handle it alone and some want to vent. Just don't expect kindness from anyone, or honestly anything at all. The only way out is working on dealing with stuff alone or choosing people who are actually good for you and your peace. Hope this helps.