From my limited experience with the Nikon, They are hot pixels and it sounds like amp glow. I find lassoing the area of ampglow and playing with it's curves prior to playing with the pictures curves a bit of a solution, but then I'm happy if i get a piccy even close to the quality of yours
My understanding is ( and it's prolly wrong ) that if you take a dark frame through a dslr your still going to get amp glow on the darkframe. I've only tried longer exposures a few times with mine and it was wholly unsuccessful, so I'm interested to follow this thread !
Keep up the great work, I think your results are excellent, for the hassles youv'e outlined with your tracking, the stars came up pretty good with only minimal distortion. Bravo !