Great picture!
I took a look in the Kilnsea Parish records at the Beverley Record Office this morning.
I found this burial:
Jan 11 1786 John Midforth farmer.
No sign of his baptism there but I did find these entries which might be relevant:
Married (apologies - just realised from my notes that I neglected to write down the year, but, from memory, it was about 1725 ish!) John Hamilton husbandman & Elizabeth Midford widow both of Easington by banns.
Buried Jan 28 1728/9 Elizabeth Medforth step daughter of John Hamilton.
I'm wondering if the Elizabeth, widow was your John's mother and perhaps he was baptised in Easington? Unfortunately, IGI coverage of Easington only seems to start in 1720 but there is one baptism on there for an Elizabeth Midford 25 Oct 1720 d/o Samuel. Again, just supposition at this stage, but could Samuel also be John's father?
It's certainly a surname that has many and various spelling variations!
Jill