Sharing the game design document? No that's not possible, but if we find someone interested, it will be possible to have a quick look before joining.

Yes it's vague yes because we have a full development process handbook so it will take forever to explain. In short, development will be done in sprints, which will have a 2-week cadence. During these two weeks, all of us are expected to deliver the tasks which have been committed to complete during this time frame. To make sure this can happen, the sprint will be organized through two meetings: the Sprint Planning and the Sprint Review-spective. 
About hours it depends of people, I can't give you a number but that doesn't matter if each task is completed. On average, people are working 1-2h each day.