As far as the crooked door, New Mexico was, and to some extent still is, a showcase of primitive skills; at least before they started getting building inspectors in modern times.
I wouldn't be surprised at all if the artist used an existing door that looked just like that as a model for his painting.
I do think he failed to get the seam right on the moccasins, and that may have made the soles look too thick, but then again, if he had someone posing, his footwear may have had seams like that.
A lot of artists will pose someone and take a few photographs, then paint from the photos. I don't know whether this artist did that or not, but it is a common technique, used by many wildlife and western artists.