1.) Yes it can power a USB hub. The hub probably takes 5v, so set the pol to 5v. Check the back of the AC adapter for something like 110/220vac-->5v dc or something like that. Then you know what it needs. And I have no idea what you are talking about when you say notorious problems for powering them seperately. THat makes no sense. Never even heard of it. The more crap you shove on 1 bus powered port, the more unstable it becomes. You are now providing each port in that hub 500mA of power regardless of what is connected before it in the usb daisy chain.
2) Yes just use the 12v line of your pc as the remote trip line for the pol. If it has a remote line. I am not really sure how that one is wired but usually it takes power, ground, and some ignition cable. Set the ignition to the 12v from your pc. That way it is triggered when the pc is triggered.