This is a long time since the last post on this complicated family but I believe Samuel (1791) was born in Wells, SOM (1851 census) - thus the son of Benjamin Callow and Elizabeth Lankey.
The 1851 census transcript (1835) is incorrect and looking at the image of the census - the age is more probably 60 (difficult to discipher) but also makes sense with the fact that someone born in 1835 wouldn't have children born 1820-1826.
I do thankyou for mentioning the 1881 census which I totally missed - as I lost Thomas Callow from 1861 onwards. Being a seaman would mean he most likely was overseas during the 1861-1871 census.
I totally agree that Thomas married Eliza Richardson of Hull.