From Kings Grant you won't have to go through the dreaded 70/73 circle. I would zig-zag over to Rt. 70 to just east of Medford and approach on Branin or Skeet Road. That will keep you out of the heavier traffic on 70 in Marlton and Medford. Personally, I've never been stuck on east 70/72 to Manahawkin because of an accident, but I suppose it happens. I'm sure that there are periodic road maintenance delays.
The alternate route is Route 532 through Tabernacle and Chatsworth to lower 72. If there were a serious problem east of there, you could always take Rt. 539 south toward Tuckerton and Rt. 9 north to Manahawkin but that would be a worst case scenario. Similarly, you could take Rt. 554 east toward Barnegat and drive south on Rt. 9.
Buying county maps and checking satellite photo's of roads are the two thing which have helped me a great deal in learning to navigate the area. Once you get out of town in the Pine Barrens, not all roads are paved; they're not all through roads.
I find it rather ironic that you can be stuck in traffic in Marlton and 20 minutes later be driving through the Pine Barrens.
NJ Pine Barrens - Your Complete Visitor's Guide to the Pinelands of New Jersey!