FINAL UPDATE: https://drive.google.com/open?id=1XOs1iFAoqR0DeZNrcUoSSCw034gCFDta
So, did some more mastering and sent it off to the judges. Hopefully they like it. The above link is the one I sent them, so you can hear the same thing they'll be judging.
Thanks @Gario and @Liontamer for the responses. Based on what you're saying, I think I'm in the clear on the sampling front. I sampled the voice clip, and a small bit of the intro to the song (a backing pad sound that plays throughout my remix but is very subtle). The vast majority of my remix is not sampled from the ost. Would love to hear your opinions on the remix itself. I've also always been paranoid that my mixing won't be good enough if I submit.
Mod review requested, this isn't a review. Just giving a heads up - I'm answering the question presented. I'll make sure this gets reviewed soon, though.
To @OceansAndrew's question, as far as sampling of the game soundtrack is concerned as long as it isn't from Square Enix there isn't a panel issue with it (Xenoblade is a Nintendo product, so far so good). However, when we look for how much source reference there is in the track the sampled portions do not count as a source reference in the arrangement. Tracks with sampled non-Square music have come up a few times in the past since I've been on the panel, and that's how we've resolved to handle audio sampling.
Sample if it makes the song sound cool (I'm personally a fan of em'), but don't use the samples as the primary source of callback to the original song; if we can't identify enough source in the arrangement without using the samples as a crutch, we will say that the track doesn't have enough source in it.
voice clips are fine, actual game audio itself (the original soundtrack) is likely not - I haven't been a judge for a few years so maybe things have changed; I recommend hitting up a current judge for the most current information.