1. I don’t like traveling with bicycles outside and feel you will age them out much quicker. I would look at some type of way to secure them in the trailer or in the cab of the truck.
2. There are plenty of racks that extend from a front receiver to the cab to carry water toys without extending back to the bed where your fifth wheel sits. You will have to get used to the overhang past the cab and adjust your position at traffic lights.
3. Owning a diesel is about the same cost as a gasser. It is the purchase cost that is sometimes hard to justify. Since you already have the diesel there is no reason to step back to lesser capable engine. Even if you can pull your current FW with a gasser, the additional range of the diesel MPG should be something to think about.