I have the 375FL, which is the identical floor plan as yours, but not with the loft above the bedroom. On mine, the refrigerator and dining table are reversed, even though floor plans show them with the refrigerator to the front and table to the back.
Beside the wall of the refrigerator, you should see a black covered plastic box. 2 Robertson head screws will remove it. The valve is behind it.
On mine, there is only 1 valve. I have a drain valve under the main body of the trailer, and I added a second drain line under the slide.
I had to replace the line under the slide because the connection started leaking. All I had to replace at the time was a standard bathroom sink flexible hose. It worked perfectly fine, but it was too long. I ordered the right length and got this one replaced eventually. It was at that time, I added a new drain for the refrigerator under the slide.
This is the main reason why I also make sure I winterize (with pink stuff) the ice maker. That line running from the frame to the inside of the slide and up through the floor is 100% exposed. No insulation, no heat, no nothing. If it's not winterized, that line freezes. I've never found a second shut off valve anywhere in mine in 2 1/2 years of ownership.