Water can flow a long ways before it finds a low or weak spot to drip out. Does the toilet rock at all when you sit on it? Can you notice it moving at all if you push it a little either front to back or side to side? If so, the seal is broken. A toilet cannot rock or it will break the wax seal. Then, with extension rings, how did you seal between it and the flange? That's another critical step.
You might be able to rent an inspection camera - these have the sensor on a long, flexible stalk. It would let you see more places with less damage than tearing out lots of drywall.