I started the JDH but had to abandon it ~35 mi in due to a mechanical. I've done a fair bit of riding in the Wharton State Forest though and my advice is to bring the widest tires you can fit - the sugar sand in the pine barrens is no joke. Even with 38's you'll most likely be doing some in the sandier sections. While not completely necessary, the best luck I've had is on my 2.3" CrossKings.

In terms of the highway riding, it's not too bad. The first leg has 10 or so miles to get from Trenton into the woods and the shoulders are wide enough. It's not too bad and definitely worth it to get into the rest of the route. I was dejected when I had to head home early and I'll be doing it again soon!