My bad.
PA stays R
There are three things for the Republicans to consider regarding Pennsylvania.
First, it's a big and expensive state to contest. If the prospects are more favorable in Wisconsin and Iowa, and it's a long shot in Pennsylvania, you've got to focus your money where it can more good.
Second, is the possibility that New Jersey is in play. If New Jersey is in play, advertizing in the Philly market covers two battleground states. Otherwise, advertizing in the Philly market is not very efficient.
Third, if the Republicans contest Pennsylvania, the Senate race may get more partisan, and there may be fewer ticket splitters. This could put Specter's seat into play. If Pennsylvania is a long-shot, there are better prospects elsewhere, New Jersey isn't in play, why increase party awareness in this state, when Specter is trying to appeal to ticket-splitters.
Regarding your Senate predictions, I think you are forecasting a net Republican pick-up of 1 seat (i.e., +GA +SC -IL = +1), with toss-up possibilities for both sides that basically cancel out (i.e., AK, CO, FL, LA, OK and SD). This means you are forecasting a Senate that is 52-48 (let's face it, Jeffords is an IINO, "independent in name only"), not 51-49.
Notice that Bush is either competitive or favored to win in each of the six toss-up states. This means that, with any up-move by Bush nationally, the Republicans could sweep all of them.