That's what is being assessed with this mission. If creating a few debris with he harpoon allows you to de-orbit the whole debris, which would have generated a certain amount of small debris over time, then it can be a win if the former is smaller than the potential latter.

Also, depending on the orbit considered, the debris generated by the harpoon may be less harmful: they have typically a high surface area/weight ratio so they will deorbit fast if the altitude is low enough, like for this mission.

Yes. It,s nearly impossible to avoid, really. Space debris doesn't really look like a problem that can be solved. It can only be managed.

Other than removed selected really large pieces, such as entire derelict spacecraft, in crowded orbits like GEO where the likelihood of hitting something else is high.