1) In the editor you can import slideshow(s) from other project files and then burn that as a single dvd. In the editor select File -> Import Slideshows. From there select a PhotoVidShow .pds project file and then select the slideshows you wish to import.
2) The extras won't be coming back i'm afraid, but only contained more background pictures etc.
3) They are plenty of updates in the pipeline. Upgrades are for free so keep posted.