If a song will not add to iTunes, generally it's because either the file is not a true audio file or is corrupt, else it is not a format type iTunes can import. There might also be the possibility it's already in your library.

BTW best way to check if files have been added is to click on the 'Recently Added' playlist.

Not sure why iTunes did not auto import the first song. Perhaps you needed to restart LW for the change to setting to work. That is true for some LW settings. Seems to vary from LW version to version.

You do need to be aware of these file sizes: Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see). Another point to keep in mind is mp3 Bit-Rates Versus File Sizes (click on link)