Interesting. I probably wouldn't have been able to figure it out if not for the video. Thank you!
The black box at 7seconds is a Ubiquiti Power Over Ethernet(POE) injector as seen here. I can't find any documentation but I am guessing your ISP is using something like Nanostation 5 as seen here. The Nanostation has 2 ethernet inputs. One is used to provide internet AND power while the other one is just internet. By disconnecting the middle power plug at 24seconds, you are turning off the power(electricity) to the Wifi antenna (AP) on the roof. That turns off his internet too. Here is a blog of a similar setup.
Who set up the Wifi antenna and the wiring outside? If it was setup by the ISP, I would suggest calling them and asking them if your neighbor has the right to be using it. Maybe the ISP installs one antenna for each building and sets up rules to share the bandwidth between you two. If your neighbor pays the ISP(or landlord) then he has a right to get mad. If not, then you have a right to be mad that he is stealing. If the wiring was done by the landlord, then I would suggest asking him if two tenants are supposed to be sharing the antenna.
Last, you look pretty close to other houses. No matter what, you may want to call the ISP and ask if you can switch from Wifi to cable modem, or even fiber. Not only would it fix your neighbor problem but it would probably be a faster/better connection. It may not be available in your area, but it's worth asking about.
Edited by Trikein, 06 September 2016 - 01:21 PM.