Well I didn't read it thoroughly but what you've asked is a trivial question. Of course you can't lose more than you have deposited (otherwise broker will pay for your losses what is unimaginable).
But in exceptional cases where broker can not close a traders' order at critical level (for example no available price at the market due to lack of liquidity) then the balance can go into negative what considering good leverage can drive you into serious problems.
Basically many brokers offer "negative balance protection" (for example I also have it at Нotforex) but the point is it can be barely seen as an advantage or privilegie for you. Events like CHF "black swan" are extremely rare on the forex market.
