1. Just use sharp side cutters, tin snips, or bull nose pliers and cut the end off. Then use a sharp box cutter or sheet rock knife and cut the plastic coating off.
2. All of your accessories and main power wire need to go to the common post on the perko, except the auto bilge should be on 1 or 2 so its on even with the perko off.
3. Yes, cut that end off and put that clamp in the pic on the end.
4. 14 gauge minimum, but 12 gauge would be ideal if you have the room to pass thru the tower IMO.