If you are tied to PHL because of airfare, then I'd just drive. The traffic on 95 southbound at that hour isn't problematic--it really only gums up south of the airport. Taking the train to PHL is slow and a pain (as you've discovered), since you have to take NJ Transit and then wait at 30th St. for the SEPTA R1.

I have lived in either Philly or northern DE for the last 15 years, BTW, and have an unfortunate amount of experience with driving I-95 in the area.