That's cool not big at all,with regards to the connection to reverse light a company selling reverse cameras supply these clips to connect to the cable is this how you would have done it?
Yes, I'd use skotch locks myself (as you've pictured) if used correctly they're the best option.
Regarding routing, pick your side and go along the sills, most of the kick plates yank off from memory and clip back into place after iirc. This'll allow you to secure the wiring with all of the cars wiring harnesses for a neat install with the piece of mind that you won't get any chafing or wires running loose