1) Why start on the PA side and walk across that nasty smoggy noisy bridge? From the NJ parking lo its about 5 miles up to the Pond on the AT, and barely 6 back on the Dunnfield trail. 11, possible 12 at MOST.
2) Much of the Dunnfield was washed out last fall with the rains. Many places have been relocated, ruining the nice creekside walk, and many of the views. I've posted questions on updates here, but have not seen any responses; leads me to believe they're still out.
3) I still agree with this routing, though I would suggest walking UP the Dunnfield Creek trail and DOWN the AT (DCT is more interesting on the way up, you cross the creek a few times, lots of blow downs...etc; the AT is just up, switchback, up, up, switchback, rather boring). Once you arrive at SFP, the backpacker's campsite is a short hike back down on the AT. From SFP you can connect with the fire trail that hooks around to Mt. Tammany and catch the views.
In the DWG NRA, there are many choices on how to hike. Perhaps plan one hike one weekend, and a different route another. Each will be different, and each will be enjoyable.
Have fun, and watch out for them wiley b'ars, mayhap y'all be needin' a skatter gunn.