Hi Alana, I showed your picture to my husband to make sure I was remembering correctly. The short answer here is that you need to call in the calvary in the form of plumbers. My parents retirement home was a 1940’s home in SW MT. They asked my husband to replace their toilet as my dad had lost his vision from AMD & wasn’t able to do the handy work he’d done for so long. So, while on a visit to them, off we all went to the big box store to buy the new toilet. My husband removed the old, original toilet & quickly determined that even a new flange wasn’t going to work bc the fittings weren’t lined up. Called the local plumber - they were able to seat the toilet with some kind of flange & all was good. Fortunately there was a second toilet in the house. My parents home was in a small town with many older homes so the plumbers were accustomed to seeing old fittings etc. I hope that’s the same situation you have - find a long established plumber who has seen old buildings.

" Are we in trouble here? Time to call in the experts?"

Yes and yes.

Agreed--we had a similar situation. The PO had done something nutty with the existing toilet to somehow get it to stay, but it never quite did and was constantly clogged, and when we pulled it off, we discovered there was no flange at all because the vintage pipe was crumbling. It was not a hugely expensive repair (though that was 10 years ago!) and was 1000% worth it--to date, the new toilet has never clogged. Our toilet location is nowhere near meeting modern code (10" rough-in with only 12" of space between it and the tub!) but that was okay because we weren't moving it, so it was grandfathered in. It was a relatively quick job.

Yes this is a plumber thing. The lead L has gotten brittle and distorted and will have to be replaced. If you have access from below through a basement or ceiling it won’t be terrible. No one will care if the clearances are too tight.