Sorry that you are going through this.
Get that you can only work on yourself. The other person may have any problems one can possibly have. But we can only work on and improve ourselves.
There are certain things I vouch for-
1. Meditation. Every day. This will be your daily sanity tablet!
2. Self care. Works wonders for empaths. Do search on it. You will get many links and videos. However, using that, you will have to find out what works for you. Slowly, have a list of things that feels good to for you. Do them often. Self care is how we take our power back!
3. Try and not take his talk seriously. I know it’s difficult. I have stopped talking. It didn’t ever help!
You need to process how you feel. You need to shoulder your own health – mental and physical. I wonder if you will find a therapist who deeply understands and appreciates both Adhd and HSP at the same time. Empaths have a need to understand, process and sort things out. ADHD personalities may not understand this. Not that they don’t want to. But then that might just to a scary zone for them. Plus they are quick to move on. It’s their good quality for negative/adverse experiences.
He is tied by his own issues as much as you are by your sensitivity. Try to see it as a mistmatch, rather than a failure.
Remember to take care of yourself!
All the best!