First I had a response from my Torongo DNA match - well, from his wife. She said they don't have much info about his family, but his sister does - and it turns out that his sister is someone I was corresponding with on Ancestry five years ago about the possible Doyle-Torongo connection. At that time, she was pretty sure about it, but I wasn't convinced, and for some reason I've forgotten, I dismissed the whole idea and stopped messaging her. How rude. Sorry about that.
So I contacted her again in hopes that she's turned over some new rocks in the last five years, and she soon responded and sent me an invitation to her tree. She had already sussed out just about everything I found about Elizabeth Doyle, and more.
I also nudged Mrs Torongo to put her husband's DNA on Gedmatch, where I might find connections with other Torongos, who aren't on Ancestry.
So where does this get me?
I'm 99% sure that the Elizabeth Doyle Torongo I've been chasing around really was my great-grandfather Isaac's sister. So there is a point in looking at her descendants, to see if there's anyone there with the same surname as PM (but don't forget, I'm NOT obsessed with PM...) And the Torongo tree I've just been given access to should be a big help with that.
But even if I don't find any likely connection to PM, I'm quite satisfied with having settled the Torongo-Doyle connection, and I enjoyed poking my nose into Elizabeth's life. Genealogy has many rewards, big and small.