As a fellow beginner, I can certainly understand your desire to trash your story and replace it with something better, but please let me add my two cents first.
Firstly, I don't think your story is bad. It's no War and Peace and it does have significant flaws, but it's not bad bad. Its flaws are obvious, yes, but all of the major factors which make a story enjoyable are strong. You have a compelling main character, an intriguing setting, a variety of different, colourful characters and a very strong plot which centers around emotions and relationships, a plot that is both rare and difficult to pull off. Just look at twilight if you want to see exactly how badly those plots can turn out when handled incorrectly.
While on the subject of twilight, let me compare the two to show you how not-bad your story is. Twilight is bad, that is undisputed fact. However, it is not considered bad due to it's grammar or style, instead it is considered bad due to its unrealistic and unemotional characters, it's disregard for lore and myth, it's contrived plot and numerous plot holes. While your story does have flaws it has few of the flaws that twilight has. Your characters are interesting and unique, I had trouble keeping track of them, but that is a matter of execution, not concept. Your characters have real emotions and they explode and overreact like all people do. I don't like them at all, but that is why the story is interesting. It's interesting to see how they begin to grow in understanding as the story progresses, even if their progress is next to nothing at the moment.
That is why I wouldn't consider your story bad. It has interesting characters and a unique plot that is genuinely intriguing and entertaining.
I'm not going to dispute your worries over your grammar. I can see that it is a bit poor, but the thing is, so is mine. Grammar is a thing that very few people understand completely, and the english language is by far the most complicated of them all. There is certainly no shame in having poor grammar if you go out of your way to learn and improve. That is what life is all about, after all. Having said that, I can see why you might want to erase your original from the internet, but I don't think you should.
Everyone has started somewhere, and if you could see some of my earlier, misguided attempts at fiction you would be equally horrified. Thank goodness they were never posted, but the thing is that I still have them. I even give them a read from time to time. While it isn't particularly pretty it is fun to look back and remember the mindset that I had when I wrote them, and to see just how far I have come since then. It's a very good feeling. Just looking at your page I can see that you have over 20 000 hits and almost 300 reviews, that's a lot of people who have taken the time to read your story felt so strongly about it that they just had to write and tell you. If you take your story down from the net then all of those reviews, rankings and hits will be gone, and you will never get them back. Don't throw away every thing that you've earned so far just because you could have done better, you might decide that you don't want to re write it, or that you can't, and by then everything you worked so hard for will be gone.
Keep your original up, even if it's flawed. It still has great value to you and to other people. It would never have made the impact it made if it wasn't.
I wish you luck in your rewriting endeavor, and may I suggest a great site to help you out; writerscrit.com .Its only a newish site, being online for half a year now but the owner there is a very exceptional person who takes the time to read and give detailed feedback to every user who submits work to the feedback center. It takes her a while, she's only one woman after all, but all together she has given me feedback for over 35000 words worth of writing, as have many other authors through the regular workshops and writing wars. It has been an invaluable resource and the quality of my writing has soared ever since I joined. I recommend it wholeheartedly.