1.- I don't know anybody who suffer these illness, but today are usual the muscular pains and I know a lot of people who feel these symptoms.
2.- I'm sure that I don't sit well and I don't type in the good manner to avoid future problems, for luck I don't stay all the days in front off the computer and only some days I work in it.
3.- Suggestions:
Keep your back right in the chair
It's very important that our elbows are at table level when we are working with the keyboard, not below or over it
Our feets must arrive at ground and not hang from the chair
The screen should be in front of our eyes, forming a range between 0 and -60 grades
You must rest regularly
4.- I think yes, there are very useful but the problem is the time that we need for doing it.
5.- No I don't eny exercise when I'm working at desk, but usually I'm doing jogging and cycling some days and hikking at the weekends