I'll answer what I can, I know some stuff.
1. No. Only a single unit, and has to be a unit that didn't fire the marker light, may use it. Once a marker
Light is used it is gone.
2. I want to say that is a warlord trait, not war gear.
3. Not sure, but sounds too good to be true.
4. With the proper use of marker lights there should be a lot less of that. There is still a lot though, and I feel the same.