Podcast Help - Using Two Pairs of Headphones on a Mac

A couple of things: Apple are notorious for removing as much connectivity from their machines as they think they can get away with - they've been doing this for a while now. The most sensible solution to your problem is to use an external USB sound device with a proper headphone socket on it - if it's a decent splitter it should work fine with that. If you get a decent device (they don't cost that much nowadays) you can even plug the mics into it and get generally better results anyway. Which brings me to the second thing...

Whatever you do, don't use the podcast template! This template has caused more anguish for podcasters than anything else I know of, and we have been warning people off it ever since we discovered just how far up a blind alley it can lead you. Thong is, it's not really a template as such - it's a load of settings applied to tracks that may have sounded alright in the rather bizarre setting they must have been created in, but for pretty much everybody else, they are completely inappropriate and will leave you sounding a good deal worse than you would have without them.

By far and away the best thing you can do is to create a basic default session with its six tracks, and if you find that you need to do anything to them, then there are loads of youtube videos that will help you achieve what you need, rather than some of the seriously screwed settings in that template.