Good work so far on the tear down.
Water may also be from the door membranes so worth checking, especially if you end up in the general area when renewing any speaker wiring.
Dim dip resistor needs to be disconnected for uprated wiring so that may be the reason that isn't plugged in.
Also, good call on the immobiliser if you do take it out. Some cars are now suffering from alarm/immobilser install on top of install (and even on top again in some cases) and it's quite satisfying taking it back knowing that you won't be stranded due to electrical gremlins.
Good luck with progress.