I struggle with  "I shall never drive dark tracks to foreign places" as well. I was able to find a good connection and meaning in a lot of the other lines but I struggled with that one. It sounds like the speaker is asking for forgiveness for not doing something wrong which, to me, seemed almost dichotomous with the theme of the poem. The line before "I shall never skip my shadow" for example, brought about psychoanalytic imagery for me, and while in Jungian analysis the shadow is inherently bad, it tends to be the less desirable traits in self. So I read that line as, I will never ignore my worst parts, I will let them grow. 
  
As for the last stanza, I loved reading it, but it seems disconnected from the rest of the poem. I understand there is meant to be a shift in tone, at least to some degree, at this point, but I feel a little more transition would benefit the poem. Perhaps another stanza between two and three. 

I really think you are on to something with this poem. It has grea

I admit -- I don't quite get it. It has the form of a psalm or canticle, with a bit of reversal going on (as if the Narrator is a Destroyer on a par with the Creator), so it has a chilling effect. But I admit I don't know what to make of "I shall never drive dark tracks to foreign places" or even the whole last stanza.

But it's food for thought, certainly.

I like it - It has a nice progression, going from begging the lord to accosting and even attacking him.

Despite that, I personally don't like the break from most lines starting with the same phrasing to the last stanza shattering that, though I can see it as a legitimate choice.

Forgive me, O Lord