...........The only other problem I have is that very fragile ribbed white plastic line that comes down from the upper part in back of the fridge. I think it may be a defrost drip line. That is what I need replaced. I can't believe that there isn't something better and less fragile than what was used. If you can determine what I am describing, do know of anything better than that?
On mine, there are two plastic tubes. One is the icemaker feed tube that you clearly have found. The other is a drain for the drip tray under the fins inside the refrigerator, not the freezer. There is no pressure on it, so it does not have to be very robust.
Oddly, on mine one day in about the fifth year of ownership, I found the drip tray full of water. Beaver left a plug in the line that should have been removed when the motorhome was built. That suggests that the drain only is active in humid climates and evaporation may be all that is necessary. In other words, unless there is an obvious problem, the ribbed white plastic line can probably wait until you get to BCS.
The freeze protection on the valve is based on the small wires wrapped around the valve. They create heat if the coach has power. If you winterize and don't plan on keeping it plugged it, you have to unscrew the hose fitting on the valve without breaking the feed line or messing up those wires.