Okay so you did pretty accurately hit most of the notes from the game, but you coud've used a midi file so I can't say much for that.

See the trouble is I can't tell if you're going for a realistic feel or just trying to make slightly updated version of the track. The thing is the low bit version of this still sounds better.

I think I'm gonna point you to one of my favorite examples a doing a lot with a little, my friend Taylor Mefford used an assortment of free soundfonts to make an amazing score. It shows you how much you can do with fx and such to make convincing instrumentation.

http://musicbytaylormefford.bandcamp.com/album/an-experiment-with-an-air-pump-original-score

I would also check out ocremix.com, they have a few helpful materials on this kind of stuff.