RE: Positive and Neg Shift
The "shift" of the FM modulation is between the TX and RX only, and has no effect when hooking up your BEC or ESC anything of that sort. So a speed control will work with any receiver, not jut one brand or another. The same is true for servos, you can mix and match brands all you want.
(with the exception of some rare off-brand stuff, I'm talking about the most common brands you'll run in to)
I don't see anything in your post that is obviously wrong in how you hooked things up. I assume you have the motor hooked up to the motor leads and the battery to the battery side and you're not backwards there? And the BEC lead to the RX, right?
As long as the battery is plugged in to the ESC, and the ESC's BEC plug is connected to the RX, then the ESC should be doing the power limiting to keep the RX from being damaged. If you have too many servos or too much battery for your ESC, then you might fry the ESC, but probably not the RX. And it doesn't sound like that is the problem.
I do agree it sounds like something else is shorted. Are the motor leads shorted or something like that?