The macerator pump will push the waste as far as it can and should not back flush into the toilet as the vanes will stop that. The downfall is you will always have waste water in the line between the pump and holding tank. One other option may be to install a one way check valve in the 1" discharge hose or 1" 1/2 line from toilet to pump, more of a insurance policy to have two systems in place IMHO considering what your working with.
