Tim, there are some major differences between your records and the Maughold parish register.
The Maughold parish register has the marriage for "1 John CANNELL" as John Cannell & Margaret Cannan married 20 Oct 1711. (No other info.) - Clearly two different surnames, Cannell and Cannan.
There are CANNAN bapts in Maughold before 1700, but no CANNELL (assume you meant b.1681) - but not in Maughold under any variation of Canel/Cannel/Cannell, except one. There is a Margaret daur of Robert Conill bapt Maughold 24 Feb 1666/67, but no John.
There is also a John Cannan junior, son of John Cannan bapt 17 Apr 1681. But definitely Cannan, not Cannell or variation.
A John Cannell appears with the bapt of his daughter Jane on 1 Oct 1709, then with John on 19 Aug 1712, Ewan on 26 Dec 1715, and James on 28 Aug 1718. There is no mention of Ballafayle.
According to the Radcliffes' book on Kk Maughold, the first John Cannell at Ballafayle was from Lonan and married Christian Christian (daur of William) the heiress of Ballafayle, and was the reason that the quarterland became known as Ballafayle y Cannell after William Christian's death. So the land belonged to her Christian family, and was not entered under Cannell before then.
The marriage appears in the Maughold par reg as John Cannall of Kk Lonan & Christiana Christian married 13 Sep 1741.
Christin daur of William Christian was bapt in Maughold Parish Church on 18 Jun 1721. (And was not the Lezayre one you noted.) The Radcliffes write that her mother was Margaret Corkill of Braddan, and that these Christians were the last ones at Ballafayle where they had been from 1624 onwards.
Christian CANNELL als CHRISTIAN was buried Maughold Dec 27 1806.
These are the only Christian/Cannell entries in Maughold par reg burials with the place name Ballafayle, before 1800:
X Ann CHRISTIAN, ballafayle, buried Nov 21 1671
John CHRISTIAN, Ballafayle, buried Aug 30 1686
John, Son of CANNELL Ballafaill buried Jul 2 1752
Edwd, Son of John CANNEL Ballafail buried Jul 6 1755
Wm CHRISTIAN of Ballafail, buried Jan 18 1759
Margaret CHRISTIAN, of Ballafail, buried Jul 7 1767
John CANNELL, Ballafail, buried Jan 25 1791
These are the Maughold bapts for the children of John Cannell & Christin Christian:
John [son of] John Cannell/ Christian [bapt] Parish Church 2 Jan 1742/43
Robert John Cannel/ Christian Parish Church 3 Jan 1744/45
John John Cannell, Ballafayle, Parish Church 19 Nov 1752
Thomas John Cannel/ Christian, Ballafail, Parish Church 4 Jul 1756
Isabel John Cannel/ Christiana Christian Parish Church 4 Jun 1759
Margaret John Cannel/ Christian Christian Parish Church 8 May 1763. Twin of Jony
Jony John Cannel/ Christian Christian Parish Church 8 May 1763. Twin of Margaret
"3 Robert CANNELL" did not marry Jane CORJEAGE in Maughold. To be sure you have the correct wife for him you need confirmation that he was from Maughold in the other parish register. The marriage on 1 Feb.1777 is in the IGI in Kk Michael as a Church Members' entry, possibly replacing an original extracted transcript. Are you sure that Robert of Ballafayle, Maughold, married in Michael and then moved to Braddan? Are there wills which support this? There were several Robert Cannells of a similar age in both Braddan and Michael.
There are no Cannell burials in Maughold on 12 Sept 1798 or on 10 Aug 1805, nor a burial in Maughold at any date for a Jane Cannell als Corjeage. There were no bapts in Maughold for children of this couple. There were however several bapts for the children of Robert Cannell and Mary Callow who married in Maughold on 10 May 1785. There was also a burial in Maughold for a Robert Cannell on June 24 1781, who could have been the Robert who was bapt 3 Jan 1744/45, unless you have evidence that the Ballafayle one moved to Braddan? There is a will for CANNELL, Robert 1781-1 Mau E w 0106396 on Brian Lawson's index which should reveal whether or not he was the Ballafayle one.
Sue