I am remodeling my bathroom and I need to add plywood to stabilize the floor before I tile, so I need to raise the toilet flange to the new floor height. When I cleaned up the flange, I see that there are these jagged peices of cast iron sticking up past the surface (see picture 1). How can I raise the flange when it is not flat like it should be? Also, there were some screws with washer-type things holding the flange to the floor. When I pulled the floor up, most of these screws pulled right out (picture 2). Should I just get some more screws and washers to screw it back down? Thanks.