Plausibility, and the limits of criticism

Eli becomes more or less accepted into the Comanche tribe. He is given a robe and his own tipi, and the Indian girl he is sleeping with is no longer ashamed to be seen with him in public, him, a white man and a captive.

Could this have happened? Would this have happened? It proceeds plausibility enough but it proceeds in a dramatic way with events clearly designed to increment Eli's status. E.g. he gains a scalp; he charges the Mexicans. He becomes accepted because it's good for the story. But given how much the Indians hate the whites and Texans in particular it just seems a bit unlikely that this would happen.

My problem is this: the world of the frontier and of native American society in the 1850s is so far from my own knowledge that I have no way to judge.

If I were determined, how would I even find out if this were plausible? Perhaps I could Google, strike it lucky and immediately find the history of a white man raised by Indians. But would it be the same tribe? Would the circumstances be the same? It's the day-to-day actions of Eli and the Indians' response that are difficult to validate against reality. Short of me reading ethnogoraphies and first-hand accounts of these tribes I have no way of judging.

I cannot have an opinion on the plausibility of this novel.