I have a hard time dealing with intrusive suicidal/self harm thoughts too. I was told that dbt helps the most with those kind of thoughts and to practice mindfulness(which you do which is good). Maybe you can go to a dbt program?

Idk how to stop the intrusive thoughts from reoccurring though. I generally try my best to think of something else and move past it, but they increase my paranoia. I try to focus on something positive and do something I like such a knitting because it requires to be focused which doesn't leave my mind to wander off. Sometimes I take a nap since naps always make me feel better.

Raw sapphire is suppose to help with unwanted thoughts. I always carry a snowflake obsidian and a raw sapphire in my pocket because it's nice to believe in something that's good for you. I hope this helps