I'll also suggest taking I-84 west in to PA, then Rt. 209 south through Milford, PA. Use the 209 south exit - do not go over to the Rt. 6 exit or you will hit bridge construction!! Rt. 209 through the Delaware River National Recreation Area to I-80 west, then Rt. 33 south. From there you have a couple of options - Rt. 33 delivers you right to I-78 and you can take this west to Harrisburg & I-81. You can also take Rt. 22 west with also links up with I-78 west. Finally would be staying on I-80 west over to I-81 south to Harrisburg - this would be my choice as Rt. 22 & I-78 see a lot of local traffic.
From I-81 take I-83 south, then Rt. 581 to Rt. 15 south. From there you can decide when & where you want to begin to work your way over to I-95. I-95 around Fredericksburg VA tends to very congested, in our experience. We've towed in and around the Baltimore & DC areas - traffic is very heavy except maybe at 3 in the morning. If there's an accident, you'll sit. Good luck & safe travels.