I should have added, yes, the blacksmith occupation is a good clue. He would probably be listed as a blacksmith or apprentice in the 1841 IOM census, and could well have gone into that occupation because of his father.

Also, the 1900 census will tell you how long the couple was married, which, would give you a clue as to whether married in U. S. or IOM.

And the date of immigration, coupled with the 1857 date in Illinois, would give you some information as to whether or not he went directly to Illinois on immigration, or perhaps immigrated earlier to some other location.