There is a will of a Thomas Fuller blacksmith of Witham dated 1830 which might be your Thomas. He mentions his dear wife Sarah. He does not name any children, but refers to" sons and daughters by his present wife or any former wife". Although not conclusive it might imply more than one former wife. His wife Sarah and son Samuel are executors.
a note on the will said Thomas Fuller died in the parish of Witham on 16 May 1829. I can't find him in parish records for Witham. Maybe a non-conformist burial.
Berks / Oxon: Eltham, Annetts, Wiltshire (surname not county), Hawkins
Dorset / Hants: Derham, Stride, Purkiss, Scott
Yorkshire: Pottage, Carr, Blackburn, Depledge
Sussex: Goodyer, Christopher, Trevatt
Jersey: Fowler, Huelin, Scott
Essex/Herts: Livermore, Holgate, Law, Day, Myson, Boyton
Norfolk/Suffolk: Stone, Alexander, Tipple, Ingate