There have been several reports of problems with the DVD-Mobile option re the current release. It is a well known fact that Fengtao (the author of DVDFab) monitors this site, and is undoubtedly aware of everyone's concerns with that option.
A new beta version is due imminently, and may correct those issues (hopefully), and your question about the multi-core speed will become moot.
Your other question can be handled one of two ways - your choice -:
1.) pm Fengtao and he'll respond directly - 'right from the horses mouth' so to speak.
2.) hang tight here and one of the more experienced members who has that answer will respond (as I obviously am unsure).