You got a tough one here. One thing to keep in mind is that for period of about 30 years after the Revolutionary War, alot of connecticut births were not recorded.
Your intention & marriage dates are correct, The intention was filed in Granville, Massachusetts. The entry in the town record book says "Sylvanus Twist of Winchester ( CT )and Phebe Barber of Granville." So Phebe was living in Granville at the time of marriage. In the vital records of Granville, Mass., Granville births, there is listed an unnamed child born 1805.
"Barber, ch. Lt. Edmund Jr. and Tabitha (d. Lt. Samuel Bancroft), Aug. 5, 1805."
There was Thomas Barber in Granville, s. Peleg and Isabell (Sherman), Oct. 24, 1783, in Hopkinton. ( Rhode Island ), died Dec. 11, 1840, Granville. Age would make him a possible brother of Edmund Barber.
The published book of the Barber Genealogy does not list your Phebe nor Edmund and Thomas Barber.
I`d suggest you research Peleg & Thomas and the Rhode Island Barbers