Can you post a photo of the bent valve handle?
Forest River uses a lot of cable actuated dump valves but not all.
Some have a rod that goes from the handle to the valve.
As mentioned, the cable actuated dump valves are prone to the cable being too long and/or mis-routed and the outer-most part where the handle attaches can be bent by trying to "slam" the valve closed.
There was a thread in the last couple weeks where a member also had the short part of the handle (where the knob attaches to a short solid rod and then to the cable) that had bent. They wound up removing the cable from the valve, pulling the lever/short rod from the outer housing and straightening the bend.
Also as mentioned, most of the time, this work requires removal of a belly panel or two.
Depending on how tough that might be, there have been some who simply cut a three sided hole in the belly. (some belly panels are rigid plastic, some are Coroplast (plastic cardboard) and some are poly fabric) If you do cut an access hole, be sure to leave the uncut side towards the front as a hinge that can then be sealed up. Leaving the front side uncut, keeps air from trying to open the hole as you go down the road.
Here's a photo showing the handle, the short rod and then the cable into the outer sheath. If you have a nut that attaches the cable sheath (to whatever it attaches to) then it it most likely a cable as in the photo.
Here is a drawing of a rod actuated dump valve with no cable.