b) is impossible, because the only low computably dominated degree is $\mathbf 0$ (see Soare's book *Recursively Enumerable Sets and Degrees*) and there are no computable nonstandard models of PA.

a) (minimal) and c) (K-trivial) are also impossible. See Theorem 4.2 of Csima/Harizanov/Hirschfeldt/Shore, *Bounding homogeneous models*. They give literature references for the fact that computing the atomic diagram of a nonstandard model of PA is equivalent to computing a PA degree, i.e., a complete extension of PA. Such a Turing degree cannot be minimal, because a PA degree bounds a 1-random degree, and the even and odd halves of a 1-random set are of incomparable degree. A PA degree cannot be K-trivial because each K-trivial degree is c.e. traceable, which implies it is not a DNR degree, which implies it is not a PA degree. See Nies, *Computability and Randomness*, Oxford Logic Guides, 2009.