Sorry to rehash, when the trailer is unhooked and the truck is sitting there, does your rear end sit higher than the front? If it does sit with the rear high when unhooked, does it sit the same way with the trailer hooked or does the truck squat and then actually appear level.
You want to try and get the same distance from the ground to the fender wells both hooked and unhooked. If it's showing lower when hooked, you might want to go up a link.
My truck sits rear end high when unhooked, when hooked I get about 1/4 of squat in the rear. I added a set of airbags and use about 20psi in them. It brings it to stock height, the trailer pulls right and it adds some support to the stock suspension stiffening it up a bit.
It sounds like you want to play with the hitch more and adjust it another link on the chain if needed. You want to go through the hitch manual again step by step. Alot of times, dealers setup the hitch and the consumer and the dealer think it's right but, it can be off still.
It still will probably take a little bit to get it dialed in but, you'll get there.
2012 Keystone Sprinter
Still sticking around for the good people and advice.