Willingham parish register baptisms 1793-1874 have been extracted onto the BVRI.
There are no baptisms of any children of William and Elizabeth, which is unfortunate.
William Frohock, father Thomas, married Elizabeth Tibbitt, father William, on 2 Oct 1761 at Willingham
William Frohock, son of Thomas and Mary, was baptised on 1 Jan 1837, along with his sisters Eliza and Jemima, so it looks as though a couple if not all were late baptisms**. There were earlier children of Thomas and Mary if you want them - just shout.
Thomas Frohock married Mary Pyke at Willingham on 29 March 1814 (IGI). Thomas Frohock, son of Thomas and Alice, was baptised on 19 Jan 1794 - which ties in with the Thomas you found in 1871 aged 77. The IGI has a marriage of Thomas Frohock and Alice Wayman on 3 Sept 1786 at Willingham
David
** His age in 1841 was 6 so he seems to have born 1834/5