Arny, thanks for your message.

What about scenario 2 where I want to combine the output audio from
the intercom and the ouput audio from my ipod and feed it only to my
headset?

Any issues there? I will be feeding stereo from ipod to the headset
so I do not need to add the 2 resistors to tie the L/R together.
Should I put a CAP on both the R and the L to keep anything from
backing up into the iPOD?

Should I do anything to keep the iPOD signal from feeding back into
the intercom via the HEADPHONE jack?

Thanks in advance!!!!

Mark