When I flush my toilet the water fills the bowl until almost overflowing and continues to swirl. Then water seeps from the bottom of the toilet on to the floor. The water eventually goes down and at the end I hear a gurgling noise.

You apparently have 2 issues, a clogged drain line from the toilet and a bad wax seal. Since you have to pull the toilet to replace the seal, why not have a plumber auger the main drain through the toilet drain and then reset the toilet with a new seal.