Stephen obviously returned to Onchan about the time his mother sold him the intack - possibly he hadn't paid for it but it would seem that elder brother Daniel had it soon afterwards - possibly there was an action at law (you mention a bloodwipe that would have got him a fine)
however the 19th Century Kewleys you are researching would appear to have owned no land nor left any useful wills so difficult to be 100% sure of descent (I assume you have checked for any MIs) until you get into the census period