If we can get the prejudice out of the way, I'm neither a "jihadist or paedophile" - I think that essentially the higher the value a crime target you are then the more likely local area thieves will put time and resources otherwise into the exercise. Please have some respect for high value crime targets :|
OK, apologies, after reading the rest of the thread I can see that you were actually serious.
You aren't being wire tapped. It would be far more practical to either compromise your PC directly and install a keylogger, thus obtaining credentials in the clear, or compromise the PC physically.
If you were being wiretapped there is no way for you to hide that you are using the internet or not short of flooding your line with spurious traffic all the time, however I'm not sure what hiding whether you are using the internet or not would accomplish.
If you are still determined that you're the recipient of an MITM attack I'd recommend a Faraday cage, as if tapping your broadband is an option so is this
Also be aware that your electricity supply is also a source of compromising emanations and you'll need to attend to that too, as well as soundproofing everything.
So you'll need to be jamming your broadband line with spurious traffic, attenuating or flooding the RF spectrum around your workstation and flooding your electricity supply with noise or again attenuating frequencies as a start.
If you really are such a high value target you shouldn't be working at home, but from a secure office location, or at very least if you must work from home work via a dedicated optical link to the Internet, meaning electrical tapping isn't possible, using TEMPEST certified hardware throughout.
Ensure you are behind a stateful firewall and never access the public Internet via your work computer. Ensure that it is on a completely different home and broadband network from anything you browse the internet with and never mix the two.
If you use a VPN to connect to work ensure that everything on the secure machine routes via the VPN, you can do this via static routing of everything through the VPN with a lower metric than the default route.
It's really all about how high value this is to you. A very high level of security costs.