Just noticed as well his year of birth is out, marriage says 30 (1781) which is backed up by the 1841 census but his death record in 1844 puts him born in 1776!
Age in 1844 census will have been rounded down to the nearest multiple of 5.
A 5 year discrepancy in age recorded at the death of somebody born in 1781 is nothing to be concerned about. Back then nobody obsessed about their exact age the way we do nowadays. Before the invention of old age pensions and other age-related state benefits, nobody over 21 had any real need to know or be able to prove their age so they tended to forget it ... just as I always forget my collar size and have to be re-measured every time I want to buy a shirt. I have no practical need to remember the circumference of my neck in inches, so I don't bother. They had practical need to remember their exact age, so they didn't bother.
Also, do bear in mind that the age at death is of necessity recorded by somebody else, and is often their best guess and nothing more. I have a number of ancestors whose age is accurately recorded in the census and then wrongly recorded at death.
