Dear SCBooth,
Just read the posts and thought of throwing my hat in here - just for one important reason - ur persistence. Like LRW said, doing the apps just once is enough to drain someone, persisting for 3 years is almost super-human! I really feel for u and pray that u don't give up on ur dream.
Now coming to what I think about here.
First, I have to agree with Cheets and LRW (although she's not gonna be a fellow Boothie!) here. The problem is OUTSIDE ur stats for sure. I don't recommend u taking the tests just as yet. It is more important to identify ur weak point(s) first. That is of utmost importance. All the suggestions given above are good; u must ask for feedbacks from schools and consultants.
Second, and this is what I just gathered after reading ur posts, u say that u have taken all ur feedbacks from ur two friends who are also ur recommenders, right?? Now, I see a lot of problems here and the MAJOR one is this - I assume that if ur colleagues have given u help on ur essays then naturally they must have helped u edit them too, right? On top of it, they wrote the reccos too. I can almost get a sense that ur essays and the reccos may be sounding alike!!!!! Giving the impression to the adcoms that u may have written the reccos ur self !!!!! Now, I am NOT saying that u did that, but is it possible that the English in these may sound similar??
One thing I can assure u is that if the adcoms get even a whiff of plagiarism or cheating anywhere, they will drop that person like a hotcake! In ur case, unfortunately,it may have been the other way round, since ur friends are writing ur reccos too!
Just have a hard look at ur essays; request ur colleagues to show u the reccos so that u can compare the prose/English/flow etc. Who knows, after reading ur essays, maybe one of ur reccomenders, in order to save time (as they all are busy), may have put almost the verbatim language in the recco too - and that is sure to spell doom.
This may be a long shot but I thought of giving u my two cents! I will be happy if my wild imagination emerges wrong but just in case it ain't, at least u know where the problem lies.
Best,
Sam