I'd put the 1000W across two blades, and the 750W across the third blade and controller. That'd keep both of them at about half power for good efficiency.
The only thing else that runs in the garage is the garage door opener, gas heat, and the water heater. The water heater is my biggest concern and I will investigate tonight when I get home what kind of power it eats up. If its too much I may be looking at another room in the house as it looks like I'm approaching max wattage. You're answer helps alot though sidehack, thanks.
Gas heat shouldn't be an issue. is your water heater gas or electric? and check the outlet that the garage door is plugged into and turn that 15 amp off in your box to see if garage door still works.
You might also have a couple 15 amp breakers that are on the same circuit. I have 2-3 15 amp breakers that run on the same circuit to prevent overload. Use that cheap outlet checker that lights up. You can get them at home depot for cheaper as well.