[Canonman]

Pretty sure you have 2 grey tanks with separate dump valves. The cavities under the trailer where these tanks are installed only allow for a certain size. Specs for your trailer show a 38 gallon black tank and 76 gallon "total" grey. So two 38 gallon grey tanks.
Like your set up, our bathroom grey dump valve is next to the black tank dump valve. Our galley grey tank dump valve is located behind the passenger side rear wheel. Easily reachable with the slide in. These handles are only threaded in to the valve or to a cable that operates the valve. They can/do come loose and fall off. I got lucky and was able to thread a new one on with minimal cursing. Also used some loctite to make sure that was the last time I'd need to worry about it.