Finally, after a week and a few companies (all highly rated on this site), I found what I was desperately searching for: a bright, focused trouble-shooter, enter Mr. Rooter’s drain technician, Travis. He was undaunted by the cast iron drain system of my Victorian. Though the house was built in 1889, there had never had an issue with the drain pipes, consequently, the cleanout, had not been touched since the plumbing went in and has sealed shut with age. No problem, Travis does a video inspection through the 1st floor toilet drain and gets to the heart of the problem in no time, and with additional locate gear, he is able to precisely define a small area of big concern (ie: pipe collapse). Before reinstalling the toilet, he replaced the worn out flange rubber gasket thing, at no charge: a good faith, great customer service gesture.
I signed on the dotted line. Tomorrow, a crew will dig out and replace of the broken drain and I look forward to reporting back with a happy ending.
I now have a ‘Go To’ guy. Other reviewers give companies a 10 when very satisfied with the service, so far Mr. Rooter, with Travis on board, rates a 20.