Cross-dimensional range just means it can go into pocket dimensions. Doesn't mean it can reach any place in the universe. Its usual range is only planetary, while Balancer spreads over the solar system, so the range is too small.
The virus isn't High 4-C, so he doesn't even need to kill that. Only needs to kill the High 4-C guys themselves. (I think
this guy is probably the strongest?)
Balancer doesn't really need NPI, as it can manipulate Information (Type 2) and with it the laws of nature themselves, including spacetime, energy and matter in general. Neither the Virus nor its hosts can survive that.
Both have too low range to destroy Balancer, while they themselves don't resist Balancer's powers at all.