Hi Bill
Glad to see you got it running, Yes for 3 axis 1 pin using 3 micro-switches, NC in series works for Limit's and homing.
When homing generally the sequence is Z then Y then X, Mach's just looking for a switch to open then moves to the next axis.
After homing thay revert back to limit function.
Yes you can use 1 pin for 2 functions (certain function's)
For a remote jog pendent I use the following.
I use pin 10 to select MPG Mode (327) and Step Jog Mode (275), switch closed one function, switch open the other, and pin 11 NO swithc to toggle MPG 1 (175) through X,Y,Z,A, Axis's.
Go to Tutorials / Documentation / scroll down to MachCustomizeWiki / scroll down Contents / 9,3 OEM Buttons, you'll See Function and OEM Code #'s
Are you talking about Start (1000) and FeedHold (1001)
Explane exactly what you want to do, If I can't help someone else will, there are so-many features with this program it's hard to be on-top of all of it.
Hope this Helps, Chip