Per pole, although I personally would not use one at the 100% rating. Watch the HP, FLA, and inductive load ratings. They are not always the same.
There's no difference. A single 3ph load of 30a would be the same to the contactor.Is a contactors rating per pole or per unit?
Absolutely, with the caveats Tom mentioned.If you have a 30a FLA contactor 3 pole can you feed three seperate 30a line to loads off of it.