Why does a planet coming toward me cause my bones to break, even before I touch it, and there exists a frame in which I'm not undergoing acceleration?

In a gravitational field steep enough to have nonnegligible tides (that is the phenomenon you were referring to, right?), there is no reference frame in which all parts of you remain at rest without tearing you apart. You can define some point in your head to be at rest, but then your feet are accelerating; and vice versa.