I'm remodeling a 45 year old bathroom and found that when I removed the old toilet that the right side of the flange where the stud that the toilet mounts to goes is broke in half and completely deteriorated on the right side of the flange. The left side is intact.

I went to HD and picked up an Oatey cast iron device that the help at home depot explains fits over the soil pipe and when tightened creates a leak proof seal. This bathroom is on a slab with no crawl access. The help at HD explained that I can break out the lead (claims it's purposely soft mat'l) that's holding the broken flange in place by pounding a 1" screwdriver around the inside diameter of the flange. I've tried this so far and while the lead appearers to be soft the old flange is not coming off. I fear really torquing down on the flange to free it, for fear of distorting the waste pipe so much that I'll need to spend big money replacing pipe tat's encased in the concrete slab......

Any help on how to release the old flange would be appreciated!