Maybe you could put a water hose down the vent pipe on the roof to see if it is clogged. Be careful, if you run water down a clogged vent, it can back up into other fixtures and flood the house. You say it wont flush. Well, if it overflows, either the toilet or the sewer pipe is at least partially clogged. If it just goes around but doesnt overflow, it could still be something small in the toilet p-trap. Or lime build up between the tank and bowl (acid through the flush valve might help). I never tried leaving a toilet loose from the flange so I dont know how that affects symptoms.