How can you increase the towing capacity of a 2007 Jeep Wr Unl 4dr 4x4 v6 3.21 gears to above 1000 lbs?

Short answer. You can't.
Towing capacity is set by the manufacturer, and no after market gizmo can change those numbers. There are too many factors. Power is only one. Braking, overheating of engine and transmission, rear end, transfer case, (4x4 only) tires, wheels, CD Player. (not really, I made that one up.) But you get the idea.
Many after market companies will give the illusion of increasing towing capacity, but they cannot.

Sorry.