While spoofing additional aircraft into the air picture is a known issue of ADS-B, blotting out the real ones at the same time is not nearly so easy to achieve as the signal is not a continous transmission.
It's also worth remembering that the near-term air to air aspirations of ADS-B are currently extremely modest. Assisting visual aquisition is one. Maintaining safe separation from a single other aircraft that has already been positively identified by ATC is another.
ILS can be jammed. But readily spoofed to a false touchdown point - I don't think so (sorry Die Hard fans).
Similarly DME. As with ADS-B the extra signals don't blot out the genuine ones because it is not a continuous transmission. So inconsistent readings yes. Consistently false reading - unlikely.
And VOR? Very difficult to spoof unless you actually build one! And a DVOR wouldn't fit in the back of your car.