Installing custom seat heaters + identifying connectors

new user here. I hope this is the right place for this kind of post.
Intro:
I own 2011 Prius (European version) and recently (as the weather went below freezing) I realised that it's time to install seat heaters. Working everyday with electronics and being a hands-on person I decided to do it myself. Ordered custom seat heater set, disassembled the seats, inserted the carbon pads, traced the wires from driver's and passenger's seats to driver's side console (probably incorrect term, see pictures below for what I mean by it) and started to look for ignition and ground connectors. That's were I ran into some problems.
1) I could not find any ID's identifying the connectors. Somewhere on the internets I've found 2010 Prius electrical wiring diagrams and it shows connectors like L6, L17, S19, etc., and how they are connected to sensors and ECU's, however there is no indication how to locate them in the car.
2) After disconnecting one of the connectors (I was looking for any way to ID connectors) I found that one pin (green wire) has corrosion (see picture below). I've cleaned most of the corrosion, however I would still like to know what pin was that and why did it corrode. It would make sense if it had some kind of external force marks or if several pins were affected, but right now it's a bit strange.


Corroded pin


What I mean by "console". It's located right below the fuses. One can see the empty black terminal where the connector with corroded pin was connected.

The heater set basically has 3 wires that need to be connected: ground/earth (ring terminal), 12V heater power wire (ring terminal + 15Amps fuse), 12V heater controller wire (no terminal). I would like to connect ground to chassis (via bolt+nut), heater controller to unused fused ignition and heater power wire to either ignition or direct battery terminal (either >=15Amp fused or unfused).

Questions:
1) Are there specific chassis tap points for ground or can I attach the ring terminal to any bolt+nut? If not, how to identify the tap points?
2) Is there any "tap" point for 12V heater power near the console or fuse box? Or should I just remove the ring terminal and connect it together with heater controller?
3) How do I identify the physical connectors/terminals with electrical wiring schematic connectors/terminals (eg. where are the 2D, L26, R1 terminals/connectors)? More specifically I want to know which pins come from unused fuses to the "console" (e.g. there are 10A fuses for factory seat heaters that are currently not used)?
4) What's the best way of connecting a bare wire (heater controller) to the "console" connector?
5) What is the function of the corroded pin and why could have that happened?

Thank you for your patience reading this post. As you can see I'm not familiar with terminology & co, so feel free to enlighten me. Also, if you have any questions - don't hesitate to ask.

 

Thanks, Chap! I've found the info I needed on that site. It's now nice and warm