Sorry to pester you with messages on a public board, but just to say that if there are any obvious errors to my research on your family, or corrections you'd like to make, please feel free to point them out to me. You can find a contact button at the foot of the home page on our website.
Our interest is in the Ruby surname but I felt it important to go back a generation to see the surname's roots and I agree with you that Ruby may well have come from Reuben. It may also have come from the meaning of Rottstein: red stone. From Isaac's record you can see the likely reason why he changed his name.
Paul