While I agree that Dick had serious psychological problems--which preceded his drug use, if I am not mistaken, I think he was schizophrenic, wasn't he?--I don't think they necessarily impacted the novel. It's a pretty straightforward piece of counterfactual fiction. I read it this past summer. I liked it much better than Do Androids Dream of Electric Sheep?. I think High Castle is better written, the plot and characters are developed better. But if I had read it, not knowing who Dick was, I think I could have thought it written by one of his contemporaries. As far as what-if fiction based on Nazi Germany's surviving is concerned, I liked Robert Harris' Fatherland much better, including the film version, though it doesn't quite come up to the novel.
I haven't seen Amazon's web series, except to have seen promos, and I don't think I'd really care to watch it. I find the novel self-contained, and don't really want to see a series based on the novel's premise, that then spins out new story lines. On the other hand, I much prefer Ridley Scott's Blade Runner to the original short story.
I think you get a better sense of Dick's state of mind from some others of his short stories. I picked up an anthology, and some of the stories are out there, in a similar vein to some Twilight Zone or Outer Limits episodes.
Prost!
Brad