This is what wards are for. It’s like throwing a drunk out of a bar only for him to stagger back in. They can’t come back if you put up a barrier, like a fence around a house so they don’t just waltz right back up to the open front door. Close the door of this metaphorical house and lock it. You can have several “fences” if you like, as well as repellent talismans etc.
Btw re the diagnosis, I’d reading more “dark triad” traits in this, like Narcissism for example. Narcs are known to be very draining and their goals are control and “narcissistic supply”. There’s tons of good info on this in yt so I won’t go on about it here. Adhd just makes you scattered and easily bored but not inherently attractive to parasites. It’s negative emotions that brings the negative entities to feed on them. Narcs don’t feel that much, so I would try to make sure you release and relax about him instead of doing all this hating, you yourself could be attracting more of these things either with or without this guy doing it.