Hoppy, Welcome to the Forum. I'm sorry that I did not welcome you before.
Before you go too far with your questions, take a little time and check out this screen saver from our friends at STI International.
I believe this will answer a lot of your questions (except the series-80).
Now on you Personal note #48: Both the firing pin and the extractor hold it in place to a degree. The trigger is not in the equation, and the slide stop plate is not an identified series-80 part.
Personal Note #50: The three fingers of the sear spring do the following (going from left to right as viewed from the rear), apply pressure to the sear, apply pressure to the disconnector, apply pressure to the grip safety.
Personal Note #51: The depressor lever does not have "sear" in the nomenclature. It (with the spring) are installed to help give the Gold Cup its fine trigger pull.
My source for nomenclature is: http://www.brownells.com/.aspx/pid=0/sid=140/schematicsdetail/1911-Gold-Cup-10mm-Gold-Cup-Combat-Target
(And on a side note: It would be polite to say "Thanks" if it is deserved.)