If you are saying you would have been able to level without the 3P hitch, then you were only a few inches out. You need to lose the Anderson levelers and get a few packages of Lynx levelers or boards to drive onto. You say one side needed to be 4" higher than the other, a 2x8 is 1 1/2" thick, so two more stacked on one side than the other.
Also be sure to position any boards under the tongue jack carefully, if the board is too wide, the spring bar from the hitch will hit it on the way down.
I use a pair of the BAL chocks exclusively and specifically for situations like this. Get 'em nice and tight between the tires and they have never failed to hold the TT at any angle. If you really want to use the wedge chocks also, use 2x8's that are cut to 4' long so you will have room for the chocks at either side of the tires. I just don't carry that much lumber with me, but may be worth it for this next trip since you definitely know you'll be using it.
Please don't dig a hole....how would like to back your trailer into a pothole that some camper dug to level his trailer? Next post would be about lack of respect for campsites....