And for Dan, you need to learn to love yourself and work on your self respect. You're far too kind you're letting people use you like a doormat. Your kindness is commendable, but the way you let people destroy you is not, don't let the only people roaming the earth the trashes, we need more good people like you but you NEED to hone your sense of belonging, respect and preservation.
It's not your fault that people are evil and trying to use you left and right. But you need to learn to shield yourself against these filths of the world. Or better yet get another guy who will protect and teach you how to appreciate and love yourself better. Although it is still better to be able to protect yourself without being too dependent on others, it's always a plus to have more protectors
Get down on your knees, apologize genuinely, then leave Dan to let him heal for good because you ARE the cause of his illness (you can help him indirectly there's no need to make him feel worse by keep seeing you and re-living the pain you caused), and go develop yourself into a better person, make amends to people you crossed when all they wanted was to help you. Until you figured it out, if you come back and see Dan again, and he's in a better place and doesn't mind you, then maybe you can try to fix the chaotically tangled threads of fate you both have. But IF Dan still find your presence as a threat or make him feel uncomfortable, then this is a tangle you no longer able to untangle and the best you can do is to not make it worse, and leave