The seats (I believe) all have backs to them.
Primanti Brothers is a definite must. The original one in the Strip is the best (IMO) and the one in Oakland is really good too. I can't say I've ever eaten at the Heinz Field one, but there is one located there...so try it out!
For any other ideas on what to do in Pittsburgh, check out this thread...It's full of good places to visit.
And have a great time...enjoy your stay and the game!