You must check J. J. Kneen's book, The Personal Names of the Isle of Man, published Oxford University Press, London, 1937, 295 pages. It is a thorough study of Manx Christian and Surname Origins and pronunciations.

Surnames are classified as Patronymic of Gaelic, Exotic, Welsh, Norman or English origin; Patronymic without prefix or suffix; Occupative of Gaelic or English origin; Local names from estates, villages or towns. Names are classified by 17 parishes. Bibliography is referenced for most versions of the name. Name origins date back as far as 1200's. The 1500's are well represented.

For example, see page 249, Watterson:
Waterson, Kirk Christ Rushen, 1511 (source Libri Assed. from 1511 onward, Manx Record Office). Watersonn(e) is a form of "Walter's son" (see Qualtrough). [Note: No reference to Quayle or Taylor].

An earlier text to check is A.W. Moore's The Surnames and Place-Names of the Isle of Man, published by Elliot Stock, London, 1890, 372 pages.

See page 96-97: Watterson or Waterson is a corruption of Walterson and a translation of MacWalter. Water is an English corruption of Walter. The Celtic contraction would be Qualtrough. Both Watterson and Qualtrough are common in the southern parishes. Watersone [1422]; Watterson [1504]; Water, Waterson [1511]; Walterson [1547]. Rushen, Arbory, Malew, German, Patrick and elsewhere.

See page 84-85: Cowley/Kewley; Scandinavian Origin. Parishes where Cowley is common, Kewley is rare and vice versa. MacCowley [1504]; Cowley [1587]; Kewley [1611]; Cowlay [1626]; Cowley-Lezayre, Ballaugh, Maughold (c) , elsewhere (u). Kewley-Braddan, Marown, Lonan (c), elsewhere (u). [Note: I don't know what c & u reference]

Most likely, you will find the answers to your other questions in these two texts. I wanted to save you from repeating research that's already been done. Good luck with your land research.