Let's see, I'll try and answer all those questions for you.
1. At home I run my 17" monitor at 1280x1024, and at work it's 1600x1024. (Cinema display)
2. I usually try to make my sites for all resolutions because I use tables. Lately, though, I've been trying out some CSS-P stuff and using layers for positioning. The minimum res. for these sites is 800x600.
3. UBB is a table. You can specify a percentage or x amount of pixels.