Some thoughts.
1) See the third question on this
page. The net install being a slightly larger CD has room for some additional packages. Therefore the available kernal will be the one used at the time the image was made. The BC version needs to fetch all packages so will always end up with a newer version. Which ever you use, you should end up with the same kernel version once install/update has completed.
2) It's because the installer already has the base packages so doesn't need to fetch them. However, the packages on the CD (like with the kernel question above) will be dated from the time the CD image was made. Post install if you run and updated apt will check every package.
3) I haven't done a fresh install in quite some. Which progress bar are you referring to? If you mean the one during get packages then it's possible it's finished downloading the required packages but before installing apt (or more likely dpkg) is building an index. But then I'm not sure I've experienced this.
Are you installing often? Ideally you should only every need to install once.
Hope that helps.