I, being a Halo Map designer and player myself, think that this so far is nothing close. A few tips though.
1) its really out of proportion. try to make it more in proportion.
2) make teleporters from each base to the center of the field on the appropriate sides.
3) dont use that worthog model ,just extract the one from the game and use that instead. I have it if you want.
4) make sure you dont forget all of the important things like the purtruding (spelling) rock off the side of the cliff walls. Just make sure it's as accurate as possible. I will definately play it.
oh yeah and make sure you get the skybox right. Make it the bloodgulch sky you can extract it from the game via Halo Map Tools and/or sapien & guerilla
what you should really do is model the terrain in 3ds max then import it. that would make it alot more accurate.