Yup, it's an amel. As for food sizes, feed something that is ~1.5x the width of the snake's widest part of its body. If its a little less that's OK, but try to avoid anything much bigger. Feed it this prey size once a week until you can no longer see a lump, then move up to the next prey size.
So if its on fuzzies now, feed it a fuzzy. If you see a noticeable lump then keep feeding fuzzies until you don't see a lump, then bump up to hoppers and repeat. Then small mice, etc. I stop at large/jumbo mice. Even if there's no lump an adult corn doesn't need more than a jumbo mouse.