My toilet is also on the opposite side. My holding tank is only a few inches in depth but stretches across the whole width of RV. Can you see down the toilet directly into tank? What do you mean you can hear it release? What is releasing? Also where is the clog...down the toilet pipe or actually in the black tank so that it's not draining?
My motorhome sensors and most motorhome sensors do not consistently work. I've used Happy Camper and toilet wand with some success. But after a couple camping trips, the sensors go back to not working. You'll just have to figure out as you go along how many days you can camp until the tanks are full.
The clog is the bigger issue. I assume this is a used MH. Maybe there is a dreaded pyramid of poo down there.