I've installed the IPD mount without much hassle. In your case are you sure that there's no remnant of the OEM mount in the ring? The outer most part of the OEM mount is made of a different material than rubber. I would say a kind of reinforced rubber which is easy to confuse with the metal ring surrounding it. try to cut it with a hack saw or steak knife. If it comes out take it. At the end you should be left with only the metal ring itself and then the poly mount installs pretty easily. Hope this helps. And one note on driving without top mount. I wouldn't do it. As far as I know the engine should not move more than 1.25" in any direction. It could damage the inner CV joints.
Ihsan