Thanks for the pics, if we continue I'll need a few more; but first -
JAXS makes a very valid point about cutting out (or better, SHARING with) the middle man - one example might be thinking that 12 volts isn't enough to hurt you - while it's true that MOST people might only feel a slight tingle touching 12 volts AND ground, if you accidentally touch 2 adjacent terminals with the same probe, you just created a dead short - under THOSE conditions, the metal part that's causing the short will become
RED HOT in 'way less than a SECOND.
This is because a decent battery that's shorted out will easily put out
several HUNDRED amps of current (think "arc welder") - I've known a few mecanics who found out the HARD way why you shouldn't work on electrical stuff wearing your wedding ring, or grab a wrench with bare hands after dropping it across battery terminals, etc -
Don't get me wrong, I'm too stubborn an old SOB to give up; but I do think you need to pick the LEAST un-informed (electrically) friend you have and get them involved before continuing.
The courses I used to teach in the military were typically 20 weeks long, with the first 6 weeks devoted to basic circuitry and component identification - if you passed that phase, the entire REST of the course was classified top secret/crypto (the highest classification in the military) - if you hadn't been vetted for that classification then you better be able to either drive a truck or cook - no exceptions -
I only bring that up 'cause either you and/or your helper need to understand basic circuits or this is gonna be one of the longest threads ever (see previous part about
"too stubborn an old SOB to give up")
This might be a good "intro", there's also the Kahn Academy site under Science but it can get pretty deep
Do you want to learn to build your own things with electronics? With this learn electronics checklist you'll see the exact steps I recommend.
www.build-electronic-circuits.com
Buckle up... Steve