Haven't had any experience similar to this with any of the demons I run into. So either its a dream or some other malevolent entity. (especially because he didn't methodically determine what they were)
I can't say that I've had demonic encounters. I've felt spiritual entities before and sensed certain presences in different places, but never anything to the degree your describing. I do know people who have had experiences your describing. They were usually resolved by telling the thing to get out.
At university I often slept very badly. One time I crept to the top floor of the mathematics building where nobody goes and lay down for a nap. I'm not sure if I ever fell asleep, but I do remember being awake, unable to move and the image of a great evil face before me, and an all-encompassing buzzing in my ears that was very stressful. My head didn't feel like it was quite behind my eyeballs. And though I could see the face I could also see the wall behind it quite clearly.
Fortunately I knew what was happening. I had read about sleep paralysis before and the hallucinations it causes. Knowing this I was able to ride out the experience with minimum discomfort and horror, and even will the buzzing away until the experience was finally over, and I could walk, quite unsteadily, home.
Conventional: He experienced a 'waking dream', temporary hallucination, sleep paralysis, etc. Like hearing someone call your name while you are falling asleep, it is not uncommon to experience strange visions when you are not fully awake.
Occult: Not likely a demon as such, more likely some other type of malicious entity. Anything from a ghost to a vampiric creature. This may be staying in the area or just passing through.
If I was called in to look at this:
A one-time incident I'm going to usually consider as something from you- dream, vision, whatever.
When things happen repeatedly, I'll look for another cause. Start with the easiest and work up.
Assume first that something is attracting opportunistic feeders and make the area uncomfortable for them using physical and energy barriers- line of salt, erect a shield.
If the problem persists, a more accurate diagnosis is required.
Begin with research on the area to determine if it could be the manifestation of a local spirit- say someone who died there. These can appear suddenly when a disturbance occurs in the surroundings, such as renovations, new roomates, etc.
Look for any physical object that has come in- these can be anchor points for spirits and removing or cleansing them may get rid of the problem.
If evidence of this appears, first contact the spirit. Attempt to explain and/or resolve the issue peacefully.
If the spirit is unwilling or unable to comply, then an exorcism/cleansing followed by a barrier to keep anything else out.
If no evidence that this is a spirit can be found, then the diagnosis moves to another astral or energy creature that can withstand common barriers.
Treatment begins with broad-spectrum magic including the use of various herbs and the like. Step one is to fumigate the house using a spiritual irritant like asafoetida and cleanse all surfaces using a the practitioners choice of magic waters, oils, etc, formulated to irritate and discourage astral beings.
After the house has been properly cleansed, a stronger barrier is set up using physical anchor points.
If the problem persists, the next step is for the creature to be (meta)physically confronted and thrown out.
If it were me in charge of the situation, I would begin by manifesting astral beings to act as guard dogs. Personally, I like to anchor them in little gargoyle figures. These creatures are either built for the purpose, or are free creatures that are enticed to help you out (or forced, but I don't do that). They are allowed to 'eat' any sort of critter that is 'negative'.
With an advanced or intelligent helper, the practitioner may be able to gain insight on the creature in question based on their description.
If the guard dogs can't eat or run it off, then it is the last resort- direct confrontation of the creature by the practitioner. In other words, a fight. And whoever is the most powerful, or at least the fastest and most clever, wins.
In some cases, this means repeating battles over and over using different tools. And failure is always an option.
If the creature cannot be removed by any means, unfortunately the only option is to move or destroy the property.