The signal doesn’t have to take down everything. Just a critical mass to take the world down. For example, if it couldn’t get the hospital, it could get the power companies nearby. Or take down the next town over and overrun the functional town.

I’m pretty sure his elevated privilege was the gun (or bomb or whatever, it’s been a minute since I read it).

The funder probably got to chose where the money went. And Kern wanted a monkey planet. I think the goal was to establish communication with them.

I think they found people were living there, and IIRC, that’s how the book ends, with them headed back to earth.

I can’t speak for the military thing. I don’t remember it well enough.