Tom's Life Bits

You can use Ember Media Manager to create the custom TV Show.
You Just Have to manually add all information then scan into XBMC

I've done a lot of what you are attempting and figured out how minimum .nfo files and they work. I suppose more items could be added but I simply want the files to show up in library mode. I am less concerned about all the metadata.

My setup is:

  SOURCE.FOLDER.for.TVshows
  ---Name.of.TVshow.folder
  ------s1e1.name.of.video.file.avi
  ------s1e1.name.of.video.file.nfo
  ------s1e1.name.of.video.file.tbn (picture shown for episode 1)
  ------s1e2.name.of.video.file.avi
  ------s1e2.name.of.video.file.nfo
  ------s1e2.name.of.video.file.tbn (picture shown for episode 2)
  fanart.jpg (background image for the tvshow)
  folder.jpg (banner or movie poster that shows up in library mode)
  tvshow.nfo

  "tvshow.nfo"
  Code:
  <tvshow xsd="http://www.w3.org/2001/XMLSchema" xsi="http://www.w3.org/2001/XMLSchema-instance">
    <title>TV SHOW TITLE</title>
    <rating>10.0</rating>
    <plot>SHOW PLOT</plot>
    <genre>Documentary</genre>
    <premiered>1969-07-14<premiered />
    <studio>International</studio>
  </tvshow>

  s1e1.name.of.video.file.nfo
  Code:
  <episodedetails xsd="http://www.w3.org/2001/XMLSchema" xsi="http://www.w3.org/2001/XMLSchema-instance">
    <title>EPISODE TITLE</title>
    <season>1</season>
    <episode>1</episode>
    <aired>2011</aired>
    <plot>EPISODE PLOT</plot>
    <displayseason />
    <displayepisode />
    <watched>false</watched>
    <rating />
  </episodedetails>

These should work for you. Sometimes when I get something wrong I have to remove my source, clean the library, and re-add the source to get it to take. For this reason I use a separate folder source for test purposes so I dont have to delete my whole library to fix a mistake with a few files.