One possibility is your browser, try using a more privacy oriented browser like Brave / Waterfox.
See https://www.privacytools.io/ for more info about browser fingerprinting.
Ultimately i think your best shot is Nordvpn tech support. That's why you pay for service.
Use this software in trial mode: http://www.hageltech.com/dumeter/about Then just open up one tab [With a single site that you wish to test] and leave it alone, then see how much bandwidth it is using while idle. That way you know exactly which sites are eating your bandwidth the most
Well, for ads I use ad block. It is quite effective and it supports all major browsers(Chrome, Safari, IE, Opera).
https://adblockplus.org/en/chrome
For system clean up, I use C Cleaner. https://www.piriform.com/ccleaner
You should also get a good Anti virus software. A good free one is Avast Anti Virus.
hope this solves your problem.
I'm assuming you are windows.
Anti-Virus - http://windows.microsoft.com/en-GB/windows/security-essentials-download
For the Adblockers are you looking for browser adblockers or are you getting adware popups?
For chrome and firebox - https://adblockplus.org/en/chrome
Using Linux, Chrome OS or macOS is a far better option than using Windows, since his software most likely won't work there. They are also more secure than Windows. You can also buy USB port blockers such as this one. Using a VPN will stop him from being able to see your network traffic.
That makes sense. What would you suggest I do to solve my problem of being able to charge and listen to music at the same time? Here is something similar to what I'm looking for, but for iOS not Android.
http://www.amazon.com/Samsung-UN32EH4003-32-Inch-720p-Model/dp/B0078LSTWU
Or you can go with something for like $20 more, 40 inches.