about to quit on a DIY project, anyone ever drill cast iron, as in 85 yr old toilet flange?

[HereSince1628]

A broken toilet flange. It's cast iron from the 1930's so it's not like it didn't serve it's time

When I pulled the toilet I found 1) the flange is soldered to the service arm...kattywampus to the floor and 2) the floor is tiled with small marble mosaic tiles right up to and on one side -under- the flange. 3) the subfloor floor was apparently leveled with some form of concrete which is almost as hard as the marble.

My original plan was built around the expectation that I could put one of those 1/4 circle flat pieces of steel under the flange to trap the bolt that holds down the toilet. But, after trying to remove a couple of the small tiles and clear away the concrete mucked in under that bit of flange, that looks like a really bad choice.

I'm not experienced with soldered cast iron and I'm intimidated about trying to unsolder the flange from the service arm or breaking it off (I really don't want to end up breaking the service arm and then needing to open the ceiling and wall in the room below in order to replace it.

Replacement PVC flanges are reasonably priced, but you've got to screw them to the subfloor, the existing flange is in the way, hence the question...anyone ever drill through an old cast iron flange?

Thanks for your consideration.