Do you happen to have a copy of the letter you mention from Simeon Briggs? I am Simeon's great granddaughter.
I just recently got JPG's of the family information in Simeon's family bible. It was mostly written down by two of his younger children (from his second wife). One of them included the oral histories she had learned.
Not everything matches what I've been able to dig up through historical documents. I've just started trying to tease out what's correct, what's incorrect, and what might just be attributed incorrectly (e.g. a single ancestor is said to have come to America with the Pilgrims and to have fought in the Revolutionary War - since these things happened many generations apart, I suspect multiple stories got condensed into a single one through time).
Any other information you might have would be greatly appreciated too! And of course if you're interested in what I have, I'd love to share.