Hi Rick,
1. A fully charged 12V LiFePo4 pack has a voltage of about 14V which might be too much for a QMX(+) when the SWR is too high (although I've powered my QMX with the exact same setup in the past)
2. Have a look at the Talentcell Powerbanks. They come in a 3A and a 6A version and provide 12V output and some USB ports.
3. Absolutely! I've been using the ATU-10 with my QMX transceivers for quite some time now.
Hope that helps!
73,
Simon
