New to us TT with Solar system. Lots of ????'s

Yes, you should run the controller output directly to the batteries, as others have implied. For your power ( 160W). and assuming you don't plan on adding panels, I'd suggest you could get by with 10 gauge, although 8 gauge would be better. No need for larger, though. Also, unless you really need to squeeze every last amp out of the solar panels I would not recommend the MPPT controller. The MPPT controller for your system is expensive and not always necessary for smaller 12V systems.