I won't give a definitive answer to the drain question...don't know that particular model, but, I would find it fairly odd to have a drain shut-off valve on the shower. You could have one, I've seen stranger things, but, I find it unlikely. If it is clogged, I would first try a bathroom plunger to see if I could force a clog out before I tried Draino or the like. If you can't get it open, Draino sitting in the pan would hazardous to try and get out by hand.
As for the pump switch, again, I'm not familiar with that model. Mine is a simple white rocker switch on the wall labeled "Pump". A friend of ours has a 2011 x-244-RBS and his pump switch, if memory serves me correctly, is mounted in a "Command Center" near the floor right at the door as you enter the trailer. The "Command Center" houses the switches for most of his ancillary equipment; electric awning, water pump, porch light, etc. along with fuses and circuit breakers.
Maybe someone with your particular model on here can chime with exact answers as opposed to my "generalizations" ?