With regards to the grey tank valve being hard to operate, I have the same problem with our 2010 MS, but I think its problem is primarily with it being cold. When it warms up, our valve opens fine. When cold, it takes two hands and bracing against the side of the RV to get it open. Generally during the winter, I leave the grey tank valve open unless I'm close to needing to dump the black tank. In our case we live full time in our MS and spend several months in each place we "stop."
As for the sewer line, we stumbled upon something called EZE-Kleen Sewer System. It is made up of proper fittings for connection to the RV's discharge line, but is flexible to use in that one can expand or contract some of the straight pieces, and a articulated set of 90-degree elbows allow the line to move right or left. A link below is to the website for EZE-Kleen, and it has a video showing how flexible the system is. However, it is not usable if there is an obstruction between the RV's sewer outlet and the park's sewer inlet.
Also, one still needs to watch that one has a down-slope of the piping to the sewer inlet.
EZE-Kleen Sewer System
We have been using this same set of piping since 2011 with only the need to occasionally replace a rubber o-ring gasket. I should add, that it isn't cheap, but to have lasted almost 10 years with no real issues, I would have probably paid more for replacement stinky-slinky hoses.
Terry