A wonderful tale so far KANACKI, reminds me of two separate incidents in my life.
When I was young I had similar dreams where I could not move and being taunted by a demon, while my room was on fire. these dreams went on and off for some years until I was able to find out the connection between me and the demon. I wrote about this some time back and it related to a past life when I was a Cathar.
I bested the demon some years back and he has not returned. The demon did not scare me so left quite upset.
The other was when I worked in a city office block around Circular Quay around the opening of the 21st Century.
I was working late, on the 13 Floor, when I felt the presence of what was a very quiet spirit and I asked "him" (I knew only that much) what he was doing and if I could help him at all.
He explained that he was guarding sacred aboriginal grounds (I did another Post on this some years back).
I then asked him if he wanted me to go, to which he said no, he just wanted to talk with me as it had been a while since anyone noticed him at all.
I asked him if he wanted to move on also, but he said he was carrying out a sacred duty and was happy to stay.
My point is that demons and/or very malevolent spirits are besides being very real can either haunt a place and/or a person.
"John" haunts a place and only females and given the dreams and the "hammer" being used against both females, John may have in the past murdered, at least one female, where the new house stands.
Given John also still haunts the area, would lead me to think he was either killed there or committed suicide.
Also, given the ferocity of John in the dreams, he may also have been an abuser of women.
As this is only the start of your story KANACKI, I cannot wait for the next installment, but hopefully the couple may pursue an investigation of what was at the site they now live in, would guess an old home and also look at old newspapers to see of any similar tales and whether a murder similar to the one in the dream.
John is a very nasty spirit.