1). From what I understand, our concept of a "Members' Gallery" is a little different from PP's. Their Members' Gallery is simply a list of all users who have uploaded images to the gallery. In vBa Gallery, you can assign any category to act as a members' category. Then any images that are uploaded to that category will automatically be placed in a "sub-category" (which I put in quotes since a category is not actually created, it just appears as one is on the user side). You can also set any category you would like to allow your members to create their own sub-categories. Any sub-categories created within a category that has been set to act as a members' gallery will also be placed under the "sub-category" that is named after that user. For a better example of this, take a look at the "Members' Category" category in the [ur=http://www.vbadvanced.com/gallery/]demo[/url]. As for assigning categories to calendar events, that would take a little work, but as long as you're familiar with PHP and can understand vB's coding pretty well then it shouldn't be much of a problem.
2). It would be helpful if I knew a little more about what exactly you were trying to do with this, but again, as long as you're familiar with PHP and vB then it shouldn't be too difficult.
3). See the answer to #2.
4). I'm not entirely sure what you mean by this...