About 1.)
I had exactly the same problem with my new DDJ-SX2. It took my hours to solve it :-( but I've found :-)
The problem is the mixing level of the rotary between cue and master. On the DDJ-SX(2) it is done by hardware in the controller and not controlled by midi commands to Traktor to the similar software rotary.
I guess the same software rotary in Traktor is turned to right, that is the master. Set in Traktor the view mode to "Mixer", the rotary is labelled "Mix" and is located below deck B at the right side. The solution is to turn the software rotary in Traktor to the left, to Cue and never change it again!!!
If you want to use that function, use only the rotary on your DDJ-SX(2), not in Traktor
You're not the first that encounters that problem.