My 1000 watt rated hub only pulls 6.7A (321.6 watts @ 48v) suggestions?
Even if you've only got around 300W, that should shift you reasonably well on the level. The limit here is 250W and that can manage 15mph with your weight on the bike, though the acceleration isn't great. But the current draw with no load (on a stand) will be a lot less than the loaded current anyway, so you probably can get the rated power or close to it. I assume it's actually rated to 1kW at 48V

The motor controller is important - is that suitable for over 20A? Is your wiring?