Paralysis, and prolonged exposure (especially to the neck or heart) can kill. You could incapacitate someone, but if not careful, could outright kill or permanently paralyze.
It doesn't really matter. If you have a Sally's store near you they sell a kit that contains clips (just make sure the clips and thread match the color of...
You need to treat all the kittens at the same time for the infection. Be vigilant with cleaning the litter boxes. If you need to separate the kittens, do so....
I would check at your local pharmacy or medical supply location for plain old Epsom salt. The scent probably won't hurt the tree, but better to be safe. Also, the...