I'd be hesitant about those backroads. If they are unpaved, they are likely sand-based and very difficult to ride on with a road bike. I remember riding back to the city Buena. The ride leader picked roads using Google Maps. One of them turned out to be unpaved for a stretch and was impossible to ride in places.
IMO, the Pine Barrens is one of the most uninteresting places to ride in this area. Incredibly monotinous. And the Wharton Forest area is not that large. You can ride through it in a day. I remember doing the organized ride called the Pinelands Triple Loop. As the name implies, it was three loops making up a century. Started from the historic village of Batsto in Wharton SF. After the first two loops I was so bored I called it a day.
If you want to go to NJ, Bull's Island and Spruce Run Recreation Areas are in much more interesting territory. (I have never been to the latter.) Hunterdon County is a beautiful place to ride. You could ride to Bull's Island for a few days and do some day rides out of the park. I have 3 or 4 cue sheets for day rides from there. The campground has some walk-in sites (you can bike in) right along the river. Walk across the pedestrian birdge and have a beer at the Black Bass Hotel.
Another NJ option I have toyed with is taking SEPTA or the NJT River Line to Trenton, then taking NJT to Seacaucus Jct. and picking up the train to Pt. Jervis, NY, where there is camping not too far away. From there, you can ride through the Delaware Water Gap National Recreation Area to Worthing State Forest, where there is camping. The next day you can ride along the river to Bull's Island and then back to Philly the following day. It's logistically tricky, but I rode the stretch coming home from Maine and it's really nice in most places. The Gap is very pretty and you might even get luck and see a bear.