as I said the Stalker name is not manx and appears only in Ramsey area c. 1820 - it may well be worth checking the only Stalker will on the Island - that of J Christopher on LDS 0106420 - that would confirm if he was the father of Thomas snr
There are only a couple of Thomas Stalkers in the IGI under cumberland in that time period - that of Thomas son of john stalker + rachel 10 DEC 1785 Saint Andrews, Penrith, Cumberland, England looks most interesting

Spouse: RACHEL ATKINSON Family
Marriage: 08 SEP 1777 Penrith, Cumberland, England

Husband Age at Marriage: 33
Wife Age at Marriage: 29

however suggest looking the will - the name maria is seldom used by the Manx - thus you are probably looking for an off Island marriage
Likewise suggest looking at the Lezayre Parish reg for the marriage - often extra info is given & also the choice of witnesses often indicative.