I'm thinking new, weed2-2 and c64 (#4, #5, #6) all seem to have a similar mood to them, and if I was in your position I would be working with these three. They have a slight sinister, searching feel to them. These three (especially new.mp3) actually remind me of some oldschool first person shooters a bit, that moment where you are wandering around a dark empty corridor ready to bump into an enemy and start shooting the place up. Faster2 reminds me of some streetfighter music, maybe it could go as a credits piece. Following on this idea, chimphell could be developed to play during an after-mission kill/score tally, and sabup_2 could probably go with an intro sequence "this is how the monsters came along, now you need to kill them" etc. Just some random thoughts.
Going by the sounds of intro and cave area you are probably going for a more positive feel than I divined from it so maybe my compass is pointing in a slightly different direction to yours. Seeing that video makes me think the music is going to get lost behind the action and sfx if it is not energetic enough, so depending on how you feel you might want to make 4, 5, 6 a bit more powerful with extra percussion, bass etc to help them survive.
I like your approach of making the pieces individually interesting with strong melodies. I also think this is something greatly neglected in a lot of modern music, and there's no reason why we can't still have strong catchy melodies with sophisticated orchestration.
Also, next time you do something like this, find a better naming system for the songs. Numbers, titles and then filenames all different to each other and with some inexplicably similar in name to others. Very confusing