Good

I feel like the pallet of the bass and bells kinda contrast each other in a way that's not complementary, also the bass sounds like it has an unintentional detuned effect on it. I see what you are going for and I like the idea, just would've liked to see a better execution.

Haha, nice! The choir in the background really gives Fallen Down a more atmospheric tone, while still keeping the original Toby Fox sound.

One quick suggestion, I'm not entirely sure if it's just me, but it almost seems as if a few of the samples you used are not transposed correctly. If this is the case, always make sure your samples are transposed. (Most of the time transposed to C)

Oh, one more thing. I believe there is room for improvement regarding mixing. The bass seems a bit too loud and the choir seems a bit too soft.