First of all, gates and even terminals for AA at DFW are pretty variable. A flight that went into C-10 yesterday and C-10 again today, may well go into terminal A or D tomorrow.

Definitely plan to connect via cell phone, or else to plan to meet at the bag claim for their flight. Meeting "at the exit from security" is too ambiguous for DFW.

You're memory is correct, there are no bars, restaurants, or shops at DFW once outside security. They've finally added some soda machines, but that's it. The exception is inside the Hyatt hotel at terminal D - that's ideal if you land at D, but if not, getting from A or C to D once airside is enough of a pain (a slow shuttle bus called Terminal Link) that it's not worthwhile for the hour or so you'll have to kill after getting your bag.

What's your plan once you meet your friend? If you'll be getting a rental car, I'd just use the time after you claim your bag to go ahead and pick up the car, then drive back to the friend's terminal, park in the one-hour spaces on the upper level of the garage, and meet them when they arrive.