I think you should work on being aware in dreams/astral realm. You are much more powerful there than here. You could confront this entity and get rid of it yourself. I will look up some works that you can learn from.
Here, I found a good link for ya: how-to-survive-and-win-an-astral-fight/ I hope it helps.
Entities are often a lower part of ourselves. The more attention we give, ie. looking for it everywhere we give it power to manifest. It's like feeding a hungry dog. It is probably a good thing to go within and look deep at anything that may have awakened that needs to be dealt with in you. I used to deal with entities all the time and learned to see about them and not give them place in my life anymore. I don't tolerate it and they don't bother me. After 2 NDE's I found out that life and the things we have been told are big lies. A lot if not most of my entities were self that I gave power to. I do use crystals and ground myself all the time as well and place light energy around me as well. I hope this helps. Also I have had many dreams come true as well about many things. I call it a gift or a for warning of sorts.
i dont know if this is still a problem but the entity is not a part of this person. a part of this person would not possess a person he loves. its a dark being. mostly i confront them and cleanse the area of their presence, and i dont use anything but my training. if i could i would do something for you but i am holding back right now as i dont know how this would be recieved. but i was trained in the use of ether and inner powers people here seem to be in tune with. i rely on my own power.
to fight the creature is complicated. its second nature to use some skill but others have to be careful. it depends on how well you sense the entity when you are aware. i dispel them while awake and asleep. although i can see them clearly over on the other side. i just trust my senses though. dark entities also have access to your thoughts and memories although its because they can read the frequencies given off by the mind. a person whom was thought dead was quote on quote visiting a group of people as a ghost knowing things only that presumed dead person knows. however things went nuts when he came home alive and well. dark entities also tend to retaliate in freaky ways so without some form of protection is it worth removing.
ill try something but i dont have a guarantee. if someone else cleanses the area it will likely dissappear and there would be no retaliation. but again being in the know makes you a target. hopefully you dont have some juicy sweet thing they want. it could be high amounts of energy, information, or just in general it wants you. judging by its past actions its the third option. since it tends to possess people it would be troublesome.
if i said what it took to fix the situation it might be taken negatively. if it didnt work ill have to wait a few hours and hope our energies intersect. sorry im not leaving the basics in skills ive placed it elsewhere and dont feel like repeating my work tonight. it should have posted when this shows up. ill leave a link when its posted.