Aside from the 4 cell issue, there is another issue. You bought a brushless speed controller that "should" run brushed motors. Further you bought a sensorless, brushless speed controller for use in a 1/12 chassis when light throttle is needed, so when you do go brushless, the combination won't work well because of the cogging. You then hooked a brushed motor to everything and now things don't work well.

In situations like this, before you change anything, or alter anything, call the company and talk to them. You shouldn't have to rig something to work. Get the right product in the first place.

Couple of suggestions:
1) buy the right product for the application (I am not suggesting that you spend $200 on a speed controller, just $100 on a new 4-cell gtb from novak, same thing you spent on the castle)
2) call the company, be nice and ask for a refund or a replacement
3) don't trash a company because of 1 bad experience.
4) the more you complain, bitch, and badmouth the company, the more the company will tell you to g.t.h.

Good luck.