Have you ever read his "On Writing"? He admits to (even embraces) the title of "America's schlockmeister", acknowledging that he writes some of his stuff merely because it sells and he has bills to pay, and takes his time crafting more deliberate works that he feels are his serious literature, but knows will not sell as well.
I agree, his stuff generally doesn't translate well to film ("Stand By Me" and "Hearts In Atlantis" being two exceptions). I'd like to see the "Dark Tower" films do well, but I don't see it being done in three feature length films, and I don't think Ron Howard is the best choice of director for these. Roland Deschaines meets Sheriff Andy Taylor.
Don’t forget about Misery. One of my favorites, and I thought the movie was pretty good, excet for a few parts that were not included.
No, but that makes sense - in that regard he's not much different from other (late) pulp era authors. But he's also much more driven than the run of the mill horror guy, in one of the biographies (can'd remember if it was "The Stephen King Companion" by Beahm or "The Art of Darkness" by Winter) he got the question "Why are you writing this stuff?". Answer: "What makes you think I have a choice?".
But the Tower was started in high school if I remember, years before anything else. Be quite interesting to see if anyone can pull it off, it does certainly have enough content. Would probably be better as a well-done series than as two or three movie-lenght segments though.