I just finished setting mine up. Since you mounted the cam plates at 18". I'm going to assume you have the round bars. If you have the trunnion setup, then that is the wrong measurement. Also, the measurement is taken from the cam pivot point to the centerline of the coupler. That said....
I would start over from scratch with the WD adjustment. You said 4-5 links. It's 5 links minimum. More is OK, less is not. Round bars perform best when parallel to the frame. Use the number of links needed to do that, again a minimum of 5 links. Check the weight transfer by measuring the fender well heights, front and back. Current thinking by the truck makers is to return the front fender to the unloaded height. Don't worry about the rear, it will take care of itself. If front and rear go down the same, great, but they don't have to. If you need more or less weight transfer, do it with the hitch tilt, keeping the 5 links on the chain. Don't worry about leveling the trailer at this point. You'll do that later by moving the hitch up or down in the stinger as needed.
Once you get the weight transfer set, then install the DC. Read the instructions very carefully. It's not rocket science, but every step is important. It really sounds like your WD just isn't set up correctly.
2013 F250 XLT
I now have a Keystone Outback, but I try to help when I can.
Bitter Gun Owner