About Star Trails:
I think you started really well. You should see my first star trails :-)
You can take some dark frames after finishing the capture, StarStax accepts dark frames to reduce noise in the final shot. You can try at 1600 to see if that helps.
About color:
You can tweak the WB of each RAW file using the sky (for example) as a neutral point. You can also take a shot of a gray card and use that as a WB reference. Then convert all the RAWs to TIFFs and stack them.
About the Milky Way:
With your Tokina 11-16 you have a great (super) lens. Shoot at ISO1600 F2.8 and test 20 or 30 second exposures checking for trails. Then you can take several shots and stack them with Deep Sky Stacker.
I wrote a small article that might help here:
http://theamazinglight.wordpress.com...apes-with-dss/