1) Shouldn't it work like this?
http://hevnikov.com/img/061113-ubuntu-partition.png
In GPartEd (which is a separate program from the installer, I think) you may have to click some Edit button to edit the mountpoint.
2) Check which video driver it's using (if it's VESA there might be problems). If the video driver is what it should be, then I guess it's the onboard video..monitor shouldn't affect that, unless it's doing the same thing for
everything and not just the video.
3) Never bumped into..can you repeat it? If you can, file a bug.