How can I remove an old waste plug from a bathtub triplever kit if the if the metal cross inside the old one is broke and the wrench made for it has nothing to grab onto?

Here is the way I do it. Use a hack saw blade with out the frame, wrap a rag around one end to make a handle. Saw the flange part of the old plug straight out from the center of the hole, saw only deep enough to almost cut through the old flange and still not damage the tub itself. Now use the blade to saw straight up and down on the inside of the flange, you don't have to be as careful about going too deep here but try not to damage the piece that you are going to screw the new flange into. When you have this cut then move over on the flange about 3/8's on and inch and do the same thing again. Make the two marks on the flange parallel to each other and not pie shaped. When you have both cuts made use a thin blade screw driver and put it flat against the tub and the blade against the little 3/8 piece the you have cut. You are trying to drive the little piece into the center part of the hole. If it does not come out with only slight tapping cut a little deeper. Once you get the piece out you then want to use the screw driver against one side of the cut on the flange and try to tap it the direction that it would turn if you were trying to unscrew it. It should break loose and start to turn. If you can not make it turn then use the saw blade again and make another cut directly across from the 3'8's gap. Then try to split it into two pieces. Take it easy, and good luck