Let me try to address each question:

‘Dropping through the zone’?? Doesn’t that mean of the ball has any kind of downward motion then it is dropping? So in all reality, if you feel a pitch ‘zooms through the zone’ it needs to be called flat or excessive speed. This is where umpires use their own lingo and it is incorrect.

No.
We tend to forget at the heart of it, this is SLOWpitch softball. A bullet has a downward motion, when a gun is fired from a level angle to the ground. Dropping/Falling thru the zone reflects the speed of said 'downward motion'.

The ball can’t land ‘deep’ (i have never called a pitch deep) because the strike zone is where the batter is normally standing
Absolutely - where the batter is normally standing (i.e., even with home plate).

So if that ball is deep, it should be also called flat, excessive speed or over the zone.
I typically say:
Ball, Strike, Short - didn't get here, Heavy - it's over him/her (meaning over the batter's zone), Through it...(meaning the ball did NOT drop thru the zone) and On it (while pointing at the plate).

And the ‘around the plate’ is about crazy also.
^^^ not sure what this is - unless you mean the 'widen the zone' part.

Always open to constructive conversations!
-LL