I will leave the wiring details to others, but thought I would respond to your questions generally.
1. I use a 45 lb. trolling motor on my 16. On a lake. This only to get away from the dock and when approaching the same after sailing, if I choose not to sail away from or back to the dock. Given the weight of the 16 (1100 lbs) I can tell you I'm happy to have that much thrust when the wind is kicking up some whitecaps, etc. Personally, I would not want to downsize. I once put my canoe trolling motor on the 16 (17 lbs thrust) and it did fine on flat water, no wind; not so well in anything beginning to feel like a breeze (especially a headwind).
2. I would not think your 30 lb trolling motor would be adequate in tidal conditions, especially if you have more than you aboard and there is any wind to speak of, and/or strong currents.
3. Keeping the battery forward is a good idea to help balance the boat. I have sometimes stored the battery directly below the companionway and brought it out and clipped it to the motor only when I needed to use it. Works! BTW, I do have a cable that runs from the area forward of the bulkhead on my 16 III to a socket at the stern, inside the boat, and have rigged a clip system to simply connect the motor clips to the socket plug. Never use it, but it's ready to use if I want to rig it up that way. I keep a battery strapped down in the bow area for lights, and use another (gel, lightweight, 32 amp) at the stern for the motor most of the time.