also i assume the stocks can be assigned once the FAZ prices falls below ...
Since you selling the puts, I don't think it is your choice when it can be assigned. Normally you have to wait till it expire. That is my understanding.
naked short 3x etf is very good as long as you have good position management and
do not need to buy back. Time is on shorter's side.
IB is good. Scottrade is shit.