Averil, I'm curious how you know for certain that this particular John (i.e., the schoolmaster of Jurby) is the one bapt 8 Jul 1781 s/o John Looney & Margaret Christian. It's possible, but there's one other option, John bapt 29 Dec 1783 Maughold s/o Thomas Looney & Isabel Moore. I've tracked 6 John Looneys baptized Maughold from 1777 to 1788, and 4 are sorted out, most of which discussed elsewhere in this BB:
1. 27 Dec 1777 s/o John Looney & Margaret Hutchin, bd 31 Mar 1810.
2. 12 Aug 1783 s/o Patrick Looney & Catharine Cowle. Md Edinor Callister 1806., bd 21 Jul 1849.
3. 10 Apr 1787 s/o Robert Looney & Margaret Cannell. Md Margaret Moore 1825 Lezayre, bd 4 Nov 1843 Maughold.
4. 21 Sep 1788 s/o John Looney & Isabel Camaish. Md Rachel Redhead & went to Australia.

That leaves the other two to fit two census entries. One could be the John Schoolmaster of Jurby that you've described. The other one could fit this one, an unmarried Tailor who died in 1860:

1841 census at Port E Vullen [? smudged] Village, Maughold 1464 7 7 pg 10
John LOONEY 55 Tailor Y

1851 census at Port e Vullyn, Maughold 2524 259 pg 19 #67
John LOONEY, Head U 68 Tailor, b Isle of Man Maughold

Burial: LOONEY, John 82 Maughold 2 Jun 1860
Family Search image: of Port y Viallin.

I don't know which one is which. The schoolmaster likely would know his age and the census and burial work out to about 1785. However, he could have cut his age a bit. The tailor is harder to determine. The schoolmaster left a 1868 will. He had no children, so perhaps mentioned a Looney relative. The 1860 John appears to have left a will too, but Ian's site points to the wrong person (I'll send him a note).

So, until we can see these wills, I'm not comfortable with the descent chart yet.