Try calling on the Archangel Michael, not to chase or banish the spirit if you don’t want that, but implore him to communicate with it to stop throwing chaos into your life.
Why do I say this? Well I was given a mantra-style method of working with the Archangel Raphael in which you use his name as a “wrap” around a person (this stuff), and I’ve seen that do some pretty remarkable stuff for me, other people (including people who had no idea I was doing the work), even animals.
The use pf the syllable Mi-Cha-El in a standard triangle of manifestation, I’m told, is a similar thing to project the will of the operator along with his or her explicit requests (such as, “Do my will but harm none” or whatever) on the entity.
And while I don’t have a belief that demons are automatically naughty and need to be kept in line, I think they’re very alien to us in some ways, therefore they don’t share, or in some cases even understand or respect, our values, and most importantly I’ve had the first-hand experience of an angel telling a demon something, which the demon was simply not understanding when I communicated about it.
He understood the words just fine (I think) but not the concepts behind them, until an angel stepped in.
So that’s my proposal if you feel like summoning this entity is making your life a little crazy, and if you do it with respect on all sides, but also the firm intent to get your needs heard, I believe it will help.
I don’t hold the belief that angels and demons are at war or even on different sides, based on what I’ve seen (though obviously they sometimes come into conflict - but then so might you and me, bidding for the same thing online, and it doesn’t mean that grudge is eternal) but again this is based on experience and please don’t take it as definitive.
I think what you need here before you do anything is some other people weighing in, I obviously don’t know everything and I have my own weird ways of working that come from being a lonely kid who figured the spirits must exist, so why not talk to them…
Anyway, to try and sum up (haven’t had any coffee yet, more rambly than usual! >_< ) I think calling on an angel to mediate and ask the entity to stay within the boundaries you set is an alternative to either continuing to put up with it, or outright cast it out, of you reallyu don’t want that.
Getting back to your buddy, if it’s an option try looking for some training in core shamanism, that focuses heavily on healing and is a useful method to learn.
There’s a concept in it called “soul loss” and that happens if someone goes through a bad experience, even a self-inflicted one like addiction or a suicide attempt: part of their soul (or overall energy) is no longer in harmony with the rest, and in the “gap” it leaves, other entities can move in - again, sometimes this is to try and help, sometimes trying to set up a symbiotic relationship, other times totally harmful.
You can expel any energies or spirits, often in a respectful way that sends them to a plane of existence where they’ll be happier, and do what’s called “soul-retrieval” and this, again from first-hand experience, is very powerful and healing.
This isn’t really stuff that can be taught on line but most trainings will pair you up with another student and you’ll do journeys for each other, which explains it all far better than words.
Sorry this is so long!