Please read these first:
http://www.8bitbrawl.com/index.php?topic=46.0
http://chipmusic.org/forums/topic/9050/
ng-advice/
as most of my general suggestions are early in those threads.
DMC vs DU sounds fine, PHF could use some compressor to give a sense of attack to the beginning of your notes, but I think both songs sound like they should. If they don't meet your desires, feel free to ask about specific details.
ADHD sounds like an incomplete song, and 99 bugs could use a hotter level (except the vocal) and slightly more stereo spread to match the others. You can't "master" until your arrangement and mix are finished.