G'day Nuvola,
I see you have a 5 speed sprocket. You may have to replace it with a smaller one, perhaps a 3 speed, even a single speed would do. With the power assistance of the motor you wont need all your gears now anyway, especailly with 1000w. I have a different brand hub that is only 400w and I could only get a single speed sprocket to fit, but I still have the 3 front gears, although I don't use them. I can still go up hill in the highest gear as the motor does most of the work. Hope this helps,
Muzza.