Your bylaws sound pretty typical - and really don't tell you anything specific. Ours, too, until we revised them recently. Here's something you might want to consider.
We gave our VP(s) the specific resonspibiilty to be the liaison between the Executive Board and our Committee Chairs. The VPs are responsible for the Committee Volunteer sign up process, for preparing our new Committee Chair folders each fall, and for conducting our Committee Chair orientation. They are also responsible for contacting the chairs each month and helping the chairs recruit additional volunteers or resolve issues that need "executive" assistance.
Specifying job responsibilities has made the role of VP much more meaningful and gives our VPs a real task to do. Some people like being VP because it's an easy (unspecified) job. We're trying to set it up so they make a real contribution with their time.
to answer your next question, our vp helps the president, for example,if the president can't be at a meeting, she/he runs it, attends school district meetings with the president, etc.
your general job duties should be itemized in your PTO bylaws and constitution. if theryre not, you need to amend them to show waht each officers job is. and now, you are in the best position to make changes to those docs, if theyre incomplete!
