1. Whatever custom form you set up for a specific category, the information/fields contained in that form are what displays on the listing page.
2. Although we do not officially support third party plugins (and hence cannot guarantee that they will all be compatible with our themes), there are many great plugins which do work well and we have some listed on our
recommended plugins page.
3. I haven't seen specific mention of anyone using JetPack for sharing, but as per the recommended plugins link above, there are some social plugins which have been tested with some of our themes. Thanks.