Way to go Doug. There's lots of info in the full shot that could be brought out with a bit more tweaking. As RB said, Flats! That's a horrid dose of vignetting you've got there.
Yep your dark frames are letting you down. Remember if the temp drop by 6deg then your dark current halves. Conversely if the temp goes up by 6 deg your dark current doubles. Not usually the problem though
ICNR can be a pain when you are doing those long shots, but with a DSLR it is probably the best way to deal with them unless you are lucky enough to have a relatively stable night temp.