Your answers ...
This question seems to be directed towards F-1 applicants - they are primarily coming to the US to study, and are not generally allowed to work. If you are on an H-1, you can study part-time without any problem. I did that, and so do many-many others.
If this is your 1st employer, then you won\'t need to list any other employer (although you might want to check with the Drop-Box guys if they need you to fill in the details of the current employer there).
The additional stuff might not be needed, as they are not part of the I-129 form itself, but documents needed to support the I-129 petition. The I-129 by itself is only 2-3 pages long.
Hope that helps - Prashant.