Hi Todd,
The key is understanding the purpose of each valve.
I have a 2007 2350 so it's going to be different than your 2010 2350. If your fridge is inside a slide out which I believe is the first year for that, that increased the differences. Still, some things will be very similar.
There are 3 valves located on the floor under the galley drawers. Pull out a bottom drawer and you will find something similar to this. During the season, the center valve should be closed, and the two side valves should be open. The valves should be reversed only when adding RV-antifreeze in the pipes. This prevents the antifreeze from getting inside the water heater so you don't fill it up.
In my 2350, inside the under-bed outdoor storage compartment, there are two valves on the far right. They drain down on the street. You can see them in this picture. When they are open along with the kitchen & bathroom faucets, inside & outside shower, the toilet lever pulled, & water heater drain plug removed, all the water in the lines drain out on the street from those two valves. The water draining process in our PC is so complete that I would never add anti-freeze in the fresh water system......there is no need for it. Anti-freeze would be needed only in the drains to fill the traps. Essential is to have the rig parked on a level surface so all the water finds it's way outside.
The last valve is the one that drains the fresh water tank. Our fresh water tank is located to the left of the storage compartment. Referencing the picture just above, the valve for that is located to the left, real close to the outside compartment hatch in a little mouse hole. The picture does not show it. It looks like a water jug valve, very cheap white plastic. For the 2010 model year, it could be located against the back wall because the water tank is located there. But I really don't know for certain.
The picture you posted does not look like anything in my 2007. Only the type of valve. Boy I dislike those valves, so very hard to turn with such a tiny handle, and I have to turn them so many times. I wish they were ball valves. Where in your PC did you take that picture?
Concerning water pressure in your PC, when using on-board water, it will run slow. If on city water, it will flow much more. If you suspect something is wrong, clean the aerator in the faucet. An indicator of a clogged aerator is if the bathroom faucet runs so much stronger.
