yeah, definitely resize those pics...it's WAAY too big. If you want, make the image clickable or use a link to go to the full size image.
why do you need to use bulb mode to keep it under 30 secs? If you shoot in M, you should be able to set a time that's under 30 secs, like 20 or 25 secs (the times, or close to, that you shot for the 2 pics above). Normally, bulb is used because you need a time longer than 30 secs.
It seems that you're a little out of focus...did you try using live view and manually focusing? I try to max out my ISO and exposure to show something in live view and just focus on any star that I can see in the screen at x10. If I can't see anything in live view, then I up the ISO and take a couple of short test shots and try to adjust focus accordingly.
The other thing is that I would probably try to increase the exposure or ISO to get more light from the shot. It seems like it's not quite enough w/ what you're currently using. I'm not sure if you're at a dark site or not though, it seems like there's some light pollution around the trees in that first shot.
Play around w/ the exposure time and see what the max is you can shoot w/out getting star trails.
If you're worried about noise, take a LOT of pics and stack them. Taking some darks (use the same settings for all the pics, but w/ the lens cap on) will also help get rid of some noise. Don't use long exposure noise reduction since you can do that at any time (darks) when the sky isn't cooperating (clouds, planes, etc).