Isabella did indeed marry Walter Gay. Of the 6 children only Walter & Flora survived and the rest died very young - I see I've recorded the death dates but not the causes of death. I did them very early in my search when I was still learning
I took a deep breath & signed up for a pay-per-view with Ancestry to have a look at the census images. They don't say much more than the index but both the Danforths & Thomas & Isabella are in Ward 6 in Springfield so they lived close to each other (the census doesn't seem to give addresses). I've not been able to find a death anywhere for Walter Gay. He doesn't show up in SP or, as far as I can see in FreeBMD in England or Wales either - son Walter moved to London, so I wondered if he ended up there if his & Isabella's marriage broke down.
There is a death of a Thomas Ross in Massachusetts in 1880 & I've asked someone from RAOGK to look at it for me to see if its my Thomas. There doesn' seem to be any record for Isabella's death but more digging may yield something. I think the presence of Isabella & Flora in Springfield (I think it has to be them) makes it almost certain that Thomas & Isabella are the right couple.
Next move is to try to find the marriage of Isabella & Levi, I think. The census shows that he was born in New York but doesn't give any birthplace for his parents.
Thanks again - I'd been hitting my head against the proverbial
Muriel