It sounds as if he and the house need a good Spiritual Cleanse. There’s the link to what there is on-site, one of those should help
But I would suggest the Cleanse and Protect Spell bath, followed by the Pure Light Houses & Spirit Clease and to top it all off I would maybe do an Ucrossing Spell.
By the way HI! I’m Amethyst from Southern West Virginia here in the States. Welcome to the forum! We’re glad to have you here and help you with your problems. There is also an Empath Shielding Spray that might help. I’m not sure if it would work on spirits or not but it can’t hurt to try.
I’m interested to see what my fellow coven members suggest. We’ll help you fix your son’s friend up in no time!