I'll point you in the right direction... Look here, under cables and power: https://en.wikipedia.org/wiki/Usb. Connect to pin1 (VCC) and 4 (GND) for 5V of up to 100mA.
You can get up to 500 mA, but if you want more than 100 you're technically supposed to ask the usb host for it. Ie, you would need a USB endpoint and get a micro to ask for more power.
Depends on the hub entirley. The USB specs say the host is supposed to shut down any port that draws more than 100ma without requesting it. Try it and find out, just don't depend on it to work on varried systems.