for people unfamiliar with PSU and the stadium on game day, I always recommend
parking at the Hills Plaza and taking the game day shuttle. It is $2.20 for the shuttle (parking is free). It starts two hours before kickoff and the last bus leaves the stadium one hour after the final gun.
The city gives the bus preferential treatment and a special lane which makes getting in and out easy. Sometimes you have to wait for a bus after the game but I doubt that will be a problem with Delaware because most people will leave well before the end of the game. The other potential downside is you can't waist too much time after the game. Sometimes you can get a food truck or hang out at the player's entrance. You can do some of this but not much.
If you want to visit downtown, I suggest you get into State College in the AM and grab breakfast along with a walk to buy shirts/stuff. then drive to the plaza and park a couple of hours before kickoff.
When you ara done and dropped off back at your car, you will be passed most of the heavy traffic for a quick breeze home. There are also places to eat in the area.