Well if you look at the DNA 30 datsheet, some of your questions can be answered.
Input Amperage (battery) requires a battery that can handle 12 Amps max.
Why not not recommend one of the two 18650 batteries that has been mentioned on this forum by mamu as well as a few other members:
The Sony 18650 30A 1600mAh and the LG 18640 30A 2500mah.
The atty resistance is 0.5 ohm to 3.0 ohms
Avoid standing in an open field or under a tree during a lightning storm, walking on thin ice, texting and driving, etc.....
Putting batteries in backwards, getting liquid into the unit, leaving batteries on charge without supervision............