I agree that Irving was never "struggling" in the sense of wanting for fame (he was the first American to achieve an international literary reputation), but he was often plagued by self-doubt and feelings of inadequacies.  I think there are some parallels, therefore, to the character of Ichabod and the author himself.

I think he may have been being playful with his own perceived shortcomings as he created Ichabod.  In his essay "The Author's Account of Himself" he talks about the "moral" of "The Legend of Sleepy Hollow."  Rhetorically asking what did the story prove, Irving responds "(t)hat there is no situation in life but has its advantages and pleasures, provided we will but take a joke as we find it; that therefore, he that runs races with goblin troopers, is likely to have a rough time of it."