I have the same baptism, for Mary Redman, as AJ plus five other possibles from the surrounding parishes.
As to her death, I have this burial at Walmer:-
Mary Matson 14 December 1755, husband William
This burial is followed on 24 January 1756 with the burial of Mary Matson, father William!
As to the death of William Matson, there are two burials at Walmer the first:-
1782 Mar 12 William Matson from Deal, and the second:-
1784 Dec 31 William Matson
Here is a piece of pure speculation; there is a long gap after Mary's death before a marriage (by Licence) of William Matson (possible the above) a Widower, to Sarah Blown in 1764. Then there is a burial for a Sarah Matson at Walmer dated 14 December 1783 from Deal!

I have not been able to find a marriage of a James Matson to Susanna.
Tony