Proof of malicious intent needed

Ever since I put up a camera system after my neighbors moved in and we had issues my internet has been regularly shut off or I have been disconnected from it. he has expressed an extreme dislike for my cameras. Every time he goes outside my internet magically shuts off. I do not get disconnected from my internet when he is not home for days at a time but that within 45 minutes of him arriving at home my internet is disabled or I am disconnected from it. This only happens when he is home. I have very odd ssids that appear on my routers AP list when these attacks happen he has a bunch of devices with extremely close Mac addresses off by one digit from one another and I cannot see his regular SSID or AP when these attacks happen. I don't know for sure this is what's going on but I have a very strong feeling this is what's going on because I had zero problems with my internet until this guy moved in and started stuff with us. If I move my wireless device to a spot in my house where I know there is metal between my device and whatever the heck he has going on over there he can't do anything to my internet but if I'm anywhere else in my house I'm guaranteed to be disconnected numerous times over the course of a few hours when he's home. I just really need some proof that he is maliciously affecting my internet and I have no idea how to get it I just want my internet back I haven't done anything to this guy he's nuts.
I can spend up to 100 bucks,.
I have a new router, with one Chromebook, one wyze cam, and one cell phone (rarely) connected to wifi. One Xbox connected via wired connection.