Hello
1. In free version of that wordpress plugin, if content exceeds height specified then you are seeing scroll bar. But in pro version there is a height options setting to set height as certain pixel value or height will be determined by content(so is no scroll) . See images in pro version demo for that setting.
2. yes in short code you can set page/group id so is you can show different pages/group in different pages.
3.Facebook has no hastag API to get posts which has certain hashtags, so in next version within a week i will add string comparisons so that posts will be shown if certain hashtag or string present in the posts.
Regards