The Kingdom intrigues me. How did the Gaelic populace obeyed so well under the Nordic rule (especially before the Norse were christianized). When did the Kingdom dissolve? Was it considered a major power in the the Britsish Isles and among the chieftains of Ireland and Scotland? Is there any king worth noticing? Hell there are so many questions. Feel free to add all you know.
I just ran into an online Celtic studies journal, issue #5 of which deals with the Isle of Man. I though you might be interested in the link. Good luck.
The New History of the Isle of Man, in particular Volume III, to be published later this year, is your best bet.
As the title of the new series suggests, there is an old book on the Isle of Man, published in 1900 and freely available online. I imagine there have been some new discoveries, or at least an update to the way the source material is approached, in the last 114 years so treat the older book with caution.
I have published on the subject of Manx immigration, which is later than our period, but perhaps you'll find some of what I have written of interest; there is this site and here are the opening and closing paragraphs of the article:
The tiny Isle of Man has had a peculiar past with its own unusual manifestation in Nevada history. Rising from the Irish Sea between Ireland and Wales, the island was colonized by Gaelic speakers in the last half of the first millennium, making its inhabitants close linguistic relatives of the Irish and the Highland Scots and more distantly of the Brythonic-speaking Celts, the Welsh, Cornish, and the Bretons of France. Viking warlords controlled Man in the ninth century, instituting a unique brand of democracy that survives to this day. The island was known for lead, zinc, and silver mines, but its economy depended mostly on agriculture and fishing. Although the island owes allegiance to the English crown, it stands apart from the United Kingdom. Man’s tailless Manx cats are well known, but a limited human population of roughly 60,000 in the nineteenth century made immigrants from the island rare. Unemployment drove people to seek opportunities off the island. Nevertheless, love for “The Dear Little Isle of Man,” “Ellan Mannin Veg Veen” as it is said in Manx Gaelic, made departing a painful thing for many.
The pattern exhibited by the Comstock Manx is distinct from those elsewhere in Nevada. While nearly all the immigrants from the Isle of Man in White Pine and Eureka Counties and in Candelaria were miners, most in Virginia City were not. Wherever they were in the state, single Manx miners followed the pattern exhibited by their Cornish counterparts: when the mines failed, they moved on and frequently left the state. Similarly, the non mining Manx, particularly when they married and lingered, again made choices comparable to those made by people from Cornwall, but as with the Cornish, married Manx who remained in Nevada were a minority. Although the Manx came from a Gaelic-speaking nation, their choices involving occupation, marriage, and transience followed the non-Gaelic Cornish pattern much more than its Irish counterpart.