I learned nothing else about Isaac Watts until graduate school. My graduate supervisor was a low-church Canadian who had left his Christianity behind but was still low-church, if you can understand this. He was a Samuel Johnson specialist, so I would say they had a great deal in common, and several of his acolytes were rather grim Canadians as well. One of them did a paper on Isaac Watts, and I finally discovered who the name at the bottom of the hymnal page from my childhood actually was.
The missal book at our diocesan parish includes a great many traditional Anglican hymns, including those by Watts. (Watts himself was not Anglican.) I observed not long ago that it had edited the Anglican words of Lobe den Herren to change the archaic thees and thys to the modern yous and yours. Last Sunday we sang the Watts words to St Anne, "O God our help in ages past", but when we got to the second stanza, I found, "Under the shadow of your throne", and things proceeded from there.
I'm a little more uncomfortable with the editors doing this with Watts than Lobe den Herren, since the Anglican version of that one is a 19th-century translation from German, while the Watts text is from Watts's hand and was intended that way by its author. By about 1705, when Watts was writing hymns, the English familiar second-person had become archaic. (The angry and unstable Hamlet was using both forms indiscriminately a century earlier.) This suggests that Watts was emulating the language of the King James Bible, which itself adopted an archaic tone to emphasize the special nature of religious language.
It's worth noting that the Ordinary Form mass mostly uses modern "you", but the Our Father continues with "hallowed be Thy name". None of this is support for the idea of a made-up BDW mass dating from 1905 self-consciously adopting faux archaism.