The flange is always dirty in my experience. I reseated two toilets the other day.

Regarding this fix. About the only thing that can go wrong for you right now is the flange breaking. I would carefully clean everything up, reset the toilet with a new seal, and then test it. If it tests good, I would use blue painters tape, and a suitable silicone/caulk to caulk around the bottom edge of the toilet. Maybe use a root killing chemical product.

You can replace the flange if you like, but this depends entirely on what kind of flange it is. PVC flanges are easy. Cast iron flanges are hard.

As far as the better than wax ring goes, I find them inferior to a heavy duty Oatey wax ring