Okay, here's how your fix medly-itis as far as I know:
*Don't cover each theme exactly, or even close to the original. Keep things like melodic and rhythmic themes, but be very flexible. You don't have much space to interpret, so use what you have carefully.
*TRANSITIONS!!! If I can tell you've changed themes, then we have a problem. You need to move between themes seamlessly enough that the listener isn't completely conscious of the moment of change.
As for what you have right now, I like the way you did Frog's theme. I also thought the voices in Gato's theme were really funny I like the thunder and stuff in Magus. Robo's theme didn't strike me as anything special. The stuff before the victory theme (which i actually didn't recognize) sounds a little thin. Victory theme is nice. End of time or whatever it's called is nice too, i like how you mixed the victory theme into it. Overall, I think you may find that you want to cut back on the number of themes to better facilitate the arrangement's interpretation. I don't believe your piece should ultimately be "theme to theme to theme to theme" etc, I think it should have a broader meaning/shape in which you use different themes (which was your first goal) to facilitate your message. I don't know what that message is tho, it's up to you
I like your guitar playing, I don't like your drums or strings. Production, as far as I can tell, is a bit shaky. Good luck!