It never bothered me to help a classmate/coworker that's part of being a team player. Be assertive if you are busy doing whatever(assessing, documenting...),say so, them them you need a few minutes to...
I would go with what is comfortable on your wrist. I've always thought bands especially plastic/poly get really hot and uncomfortable, and like a bracelet strap, plus a good stainless watch you can...
Like others have said it depends on the program. Check the requirements for the program you're interested in, some use last 60 credit hours for gpa, others use your entire academic