Randyj,
Too be honest, when I first saw you state, "...and cut the safety ground from the switch box..." I immediately cringed. I am an electrical engineer, degreed from a major university and with a state license, and I find myself having to walk very carefully through the types of things you describe before I change anything like an existing safety ground.
I have seen some references elsewhere to a long distance distributed system like this having multiple grounding rod locations. Perhaps this is what you refer to. But, I would think that the ground rods back at the house should still be connected to the ground wiring, just the dock ground rods added to the system. If you have any neutrals at the dock tied to ground, than perhaps you have the neutral-to-earth voltage differences due to voltage drop across the neutral return as you seem to want to describe. But, perhaps you have a short somewhere on the dock using only the ground wire. Or maybe a nearby dock has a short with your dock's ground providing the return. Tread carefully, there could be a number of reasons why you could see this tickle voltage. And, lifting grounds could be the worst solve for them. ActionDave's link is very sobering
Maybe upsizing the cable back to the house above what would otherwise be required by code may be part of the solution. But, I think you really need some expertise to figure this all out. With so many docks on the lake, maybe there is a really sharp electrician locally who specializes in this. Ask around.