I agree that the plot is good, and also that it needs editing. Something like the browser extension Grammarly can catch quite a few errors. A word of advice though, it tends to make the text editor on FiMFic unbearably slow, so I'd recommend writing a bunch with Grammarly turned off and then turning it on to fix any errors.
I hope you don't mind, but I copied the prologue of your fic into Grammarly's text editor and this is what came up. I don't know what the premium alerts entail since I don't use the paid version, but even so, that's 13 less errors that an editor has to fix and 13 less errors for a reader to see.
I've already got a lot on my plate between my job, BronyCon coming up soon, and the three fairly large fics I'm currently working on. I don't have time to do a lot of heavy editing in addition to all of that. I could do a little bit for you here and there if you want, but it won't be fast progress.