Same problem here-----2016 Ram 4X4, CC and a Cougar fifth wheel.
I can't lower the hitch because the pin box will hit the truck bed. What I did was to have a trailer builder weld up a 3 inch box sub frame between the shackles and frame. It looks good and "almost" levels the trailer. There is still a two inch rise in the front, but all works well. The trailer tows solidly with no sway.
The extended shackle fix looks a little spindly. We followed a fifth wheel Cougar for a few miles (with longer shackles) and there seemed to be some unexplained movement with the unit.
This spring, we might look into larger tires on the trailer.
What ever you choose to do---you will be stuck with it, so choose wisely.
