Ultramax Install over poor flooringl installation...Pics

[tesla]

Ultramax II base is longer and narrower than the one it replaces. Fake wood was installed around the toilet so that the toilet sits on the concrete inside of the flooring. The front edge of the base is right on top of the edge of the wood floor and there are gaps on the sides. The back 2-3 inches of the base sits squarely on the wood. I need to fill this cavity up with something for aesthetics and stability of the toilet. I may replace the floor with ceramic tile as much of the wood around the toilet is water damaged. Any ideas?

Also, will I need 2 wax rings or an extra large one for this since the flange is on the concrete? I have an extra large with horn.

Toilet pictures are dry fit without wax.