Hewitt Griswold and Betsey

Does anyone knows more information about Hewitt Griswold?
All I can find that he was born 10 May 1774 in Lebanon, Grafton, New Hampshire and being the son of John Griswold and Ruth Hewitt.My problems are:
1. I don't know who his children were.
2. He married Betsey Howe in 1833.She was born in 1815.
Why would an 18 year old girl marry a 59 year old man?
3. I see he was married to an Abigail.Could Hewitt and
Abigail have a son Hewitt Jt. and it was he who married
Betsey? (Betsey Howe)