Does this mount at the factory rocker points or require drilling?

This uses factory mounting points—no drilling required. Bolt it into the existing anchor locations and you're done.

Will this work if my bumper cover has sensor holes in it?

The reinforcement bar is behind the cover. Sensor holes in your bumper don't affect installation or function of the bar itself.

What if my bumper is damaged—do I need to replace the reinforcement bar too?

If the bar itself is cracked or bent, yes—replace it. If only your cover is scuffed, the bar is fine to reuse. Inspect it before reassembly.