Someone please HELP!!

The toilet in our only bathroom was "rocking" badly. What I originally thought was only a bad waz ring or a broken toilet bolt turned out to be THREE broken anchor (flange) bolts. This would be an easy enough problem to fix except for one catch...the floor is concrete slab.

The drain pipe is standard 4' pipe but I'm not certain if it's lead or ABS. My first question is how much space is required around the waste pipe for air circulation?

I bought a new 4" closet flange to replace the older one but the "rim" of the drainage hole is sloped at different angles as if the old bolts cracked the concrete so drilling holes for the flange is nearly impossible as is. My other question is can I patch the concrete to certain dimensions to redrill holes for the floor (closet) flange?

Any advice will be appreciated. I've almost pulled my hair out with this problem.

Thanks,
Anita