You can always tell which of the members are married, lol. I speak from experience, of course
lol: Not married, but I have a girlfriend of a year-and-a-half. I've learned who's boss
As far as the story goes, I'm not so sure; I mean, it's possible, as there are at least three canon incidents of the Tuskens adopting those they've captured; Sharad Hett, A'Sharad Hett, and Tahiri Veila.
But Tuskens are not supposed to be portrayed as the type who would adopt others into their culture on a regular basis; they do not trust outsiders, especially given the environment of Tatooine itself. They war against moisture farmers, and slaughter those they come across, leaving none alive if possible.
Call me an EU snob, but it just doesn't seem believable from a canon perspective.
For the blood-smear, what you could do is paint the palm of your hand, as well as your fingers, with blood-red paint (or even brownish-red), and drag it across the helmet to give it a realistic, ritualistic look.