Run the file through MediaInfo (I posted link above) , set it to text mode, and post that info here.
Knowing what you are dealing with will help figure out why you are seeing bad-looking video.
non-free solutions:
ConvertXtoDVD should make the entire file into a DVD (or several files, and regardless of their resolution).
VideoReDo will probably let you edit your file, trim the ends, take out commercials, and their Quickstream Fix feature will clean up most dirty video.
It can author DVDs, too, plus they have a good support forum.
They have a free (you need to register it) test mode with full capability, so you can try before you buy.
If you are technophobic (and don't want to learn the editor), ya might be better off with ConvertXtoDVD or some other solution.