Rid-X will not do anything unless you leave it for 30 days or more with plenty of water. My best suggesting is to get one of the clear sewer outlet connections that allows you to connect a hose which blow a stream of water up the outlet. This will pick away at any blockage and you will be able to see when fluids start flowing properly. Once you have an open drain you can work on the other solids which may have accumulated inside the tank. That's done with lots of water. You should be able to look down the toilet opening to see if there is a pile down there and you can flush from inside as well to get rid of that. Once the major issues are taken care of you can add water and drive. Even if you don't get it all at this point, it will get better and better over time as long as you flush with plenty of water at every flush. I would flush 2 full bowls anytime you are making a solids deposit. Don't dump until the tank it 2/3 - 3/4 full and start all over again.