Trouble deriving a BIP 32 Child Key
Ended up answering my own question! If anyone else runs into a situation like this, the problem is that the code is deriving a non-hardened child key but checking for the hash associated with a hardened child key. According to the BIP32 docs, to derive a child key you hash the private key prepended with a single zeroed out byte and appended with a hardened index (greater than or equal to 2^31). So in this case, I only needed to swap out the public key for the private key, prepend it with a single 0x00 byte, and use the first child hardened integer 0x80000000 instead of 0x00000000.