Very helpful information indeed - great detective work!
You have found at least two other sources for this flag silk that I had not located. When I told the late Howard Madaus about the Watkins & Ficklin invoices (be sure to get those from Footnote) he calculated that only some 80 flags or so could be made from the silk that Selph bought from them. So your finds may fill in the blanks for the balance of that silk. We always knew that there would be a couple other firms selling bulk dress silk and I had a long list that I was going to work through over time to find them. Thanks for doing so!
The bolts were, I believe, 18 inches wide. I will have to dig into my files and see Howie's email on the topic and can post that information here when I find it.
Again - great job!