I disagree with your conclusion about Joseph's parents (or at least I think I disagree with it)!
Joseph was 51 in 1841 and 60 in 1851, which ties up exactly with the baptism in Arlesey on 20 Jun 1790 of Joseph, son of Thomas and Mary, so I'm sure we agree so far.
Where we part company is the interpretation of the children baptised in Arlesey with parents Thomas and Mary. I too drew up a list of these children, starting in 1788 with Edward, followed by your Joseph in 1790. It hit me that there was another Edward in 1798 but no burial of an Edward son of Thomas and Mary in the ten years between. Why would they name a second Edward if the first was still alive? Two different families is one answer. When I found that Thomas and Mary Lyne didn't marry until April 1793 (with Thomas being a bachelor, not a widower), with three children already having been baptised up to nearly five years earlier, my conclusion was that there were probably two Thomas and Mary couples in Arlesey, the earlier pair possibly being Thomas Albon and Mary Toaken who married in Shillington in 1788.
And it's trying to prove that hypothesis that I've been working on over the weekend (and I'll probably be asking for John's help in Bedford Archives when I finalise what it is I need eg marriage witnesses which the transcripts don't show.)
I think that Thomas, the father of Joseph, died in Arlesey aged 62 in 1830, whereas the other Thomas, son of Abraham, was alive in both the 1841 census aged 70 ie 70-75, and in 1851 aged 83
It would help if I could find either Mary Toaken or Mary Lyne!
What do you think?
David