From your question, it occurs to me that you already have the following information, but here it is anyway.I haven't discovered yet if Silas and Sarah had children.
Gustavus Norwood, son of Caleb married Mary Milbury in 1742. Mary died in 1819. She was a dau. of Samuel. A Bragdon diary states widow Mary Norwood died Dec. 20, 1819 at age 99. Gustuvus was an Innkeeper and lived at York Harbor. Gustavus and Mary Norwood had the following children; Samuel, 1743-1819, married Mary Raynes; Alice, 1745- ?; Gustavus (sometimes Augustus), 1748- ?; Sarah, 1751- ?, married Silas Derby, 1745- ?
Caleb Norwood, father of Gustavus, was a son of Francis Norwood, the immigrant. He married Alice Donnell.