Just a thought regarding your Griffith ancestors. I have a great great grandmother from Llanrug called Mary Griffiths born late 1700s - her father was a Griffith Prichard. This is where the dreaded patronymics come into play. It was used in Caernarfonshire and Merioneth until the early 1800s.
So you have to check carefully as Mary was given her father's Christian name for her surname. ie Mary daughter of Griffith Prichard. Mary verch Griffith in Welsh. Her brothers too. They lived in the Bryngwyn area of Llanrug and are on the 1841 and 1851 cenuss. There isnt a Hugh though. Good luck happy new year and regards