I have audio recordings of my neighbors speaking over my computer speaker (that match the audio/video recordings of their other harassments), and experience the same wrongful acts after I change passwords. I even experience them changing passwords, after I just changed a passwords, recorded in Keychain access. If I knew the "technical" explanation, I would have stopped it already. But, again, as they aren't very bright, these are just small cheap tricks which are easy to do, thereby easy to fix. Nothing they do is "rocket science", they are incapable of anything complicated. I just haven't come across the cheap trick fix, just yet, not spending much time on it. As usual, I'll come across the fix without much effort. However, in the meantime, it produces a ton of legal evidence, and will be used in legal proceedings against them in the near future.
How is your neighbour putting audio over your computer speaker?
Its really difficult for someone here to help you. You mention changing the MAC or disabling NetBIOS but you don't explain how you think those things will help you. You mention that you think they're remotely controlling your computer but you don't mention how. You mention that they're slowing down your Internet service. That's really not likely, unless they're just hammering your link with traffic.
It appears you have some knowledge but your application of the knowledge might not be correct.
I recommend you get a security professional to help you.
Assuming you're not going to do that, then I would backup my computer and backup my router. Then I would reset my router to factory defaults and reconfigure it, ensuring that it's secure. Disable wifi, disable remote admin, ensure you have a strong password, ensure the firmware is up to date. That will close most holes there.
On your Mac, I would make a backup, wipe and factory reset, and then do not restore you data. If your system is compromised and you restore your data you may be restoring compromised apps. Just make a backup, put it aside, and get to grips with cleaning this mess up first.
You'll then have a relatively clean network and Mac (from what little we know about the setup). Then as these things continue to happen you can document them and we can try to help you.
I wouldn't knee-jerk to trying to change MAC address or disabling NetBIOS etc. I don't think these things are likely to help you.
This may be something as simple as a bluetooth connection to your speaker, but you don't mention anything about the physical layout (how far are your neighbours) or how your speakers are connected.
Again, I recommend find a security professional. If this turns into a legal thing then they might be an expert witness too.
