If you got the tools, what you do is drill holes about 1/4" bigger than what screws that you are installing. Then get a resin fill that you can find at your local hardware store. Fill that up and let it sit to near solid. Once it gets to that texture, put the screws in and let the resin dry around it. That should solve your screw problems.
From the pictures, if the pipe is on uneven ground, lift those 4 pieces of tile around the pipe and sand it out. Then use that resin or some form of concrete to make a new surface. This is a bit time consuming, but it will fix your wobbling problem. Id do it myself if you were local. :/