Good start. I can feel your determination.
FYI, while I hear your desire for low ISO, you could go up to 200 or 400 with very little noise or degredation of image quality. It's the higher ISO numbers where one gets more noise with the increased sensitivity. With a bump in ISO you could easily shorten your shutterspeed. 1/6th is too long to stop motion. I personally can't handhold with that long of a shutterspeed and would need to use a tripod and remote shutter release.
I see you're using Lightroom 3.5. 3.6 is available. While in zoomed in on that streak in Develop, click on the Spot Removal tool and Clone for Brush. Center the cursor over the streak, spin the wheel on your mouse to adjust the circle diameter to include the streak and a bit more, then click, hold and drag the "source" circle around until the target circle (containing the streak) disappears, then release. Bye bye streak. There are several other bits of marine snow needing removal as well.
Definitely keep shooting in RAW. It is much easier to white balance and one can also change exposure after shooting. Try that with a jpg. In RAW, the information saved out is the data from the image sensor without any of the usual automated process of the camera, such as white balancing, conversion to jpg and compressing. That leaves you, the human with vastly greater visual accuity and perception, to make those decisions. And usually that's a very good thing. Shooting under high color temperature lighting may be a reason to start using RAW, but soon you'll want to shoot everything that way.
In my opinion, the dark area in the zoos is a bit too strong. I would consider lowering contrast some and / or using the Shadows slider in the Tone Curve section in Lightroom.
If you keep getting into it, eventually you'll wonder if your monitor is actually displaying images properly, and how can you make aesthetic calls on image exposure and color if it's not? That's where monitor calibration devices come in. While you can't be sure the person viewing your image on their computer has a properly calibrated display (and they usually don't!), you can at least be sure the image you're producing is based on your calibrated display.
Keep it up! Post more pics, especially one's your having trouble with. It's those images that can provide the greatest learning opportunities, as they encouraging thinking about how to make it better.
