Marine/RV toilet paper is fine for flushing in a marine/rv head, provided you're not tossing basketball sized wads down there. Residential TP is NOT recommended in a marine head system.
Fuse is a good place to start. Meter the pump and se if you get voltage when someone is pressing the button. They might have burnt the pump out.
Incidentally, if the blackage is in the line between the head and the tank, then pumping out the holding tank would not fix the problem. It would only empty the holding tank. You're going to need to make sure the initial blockage is removed from the system. (You're gonna need some rubber gloves