Good grief, hahaha, all this hassle over my overlooking things, lol...
Turns out it was R169 not being soldered in good. One of its leads is so close to one of the R187 leads I removed that the heat from my desoldering gun must have weakened that R169 leads connection.
Anyway, I resoldered that lead, turned it on and finally it comes on in receive mode, and it does key up as it should when I press the PTT on the mic. Everything is now back to working as it should.
I'm still gonna run some voltage tests in the mic amp area, regulator area, Passthrough area and RF stage area to be sure nothing got weakened further.
Note to self: pay more attention to surrounding areas of the area you're working in.
Thank you guys/gals, you're all the best.