I think you are in the wrong way. the answer of this puzzle in not a brainwallet. let me explain:
each 64 byte hexadecimal number can be a bitcoin private key. for generating a bitcoin private key from a 32 character plain text we have 2 options:

option 1: a brainwallet: we calculate sha256 hash of text. the result is 64 byte hexadecimal number. in fact result of calculation of hsa256 of any text with any length always is a 64 byte hex. then in this option the length of text is not necessary be 32 character.

option 2: we convert each letter to its ascii code. the result of converting each English letter to its ascii code is a 2 byte hexadecimal number. then converting a 32 character text to its ascii code is a 64 byte hexadecimal number.

according to the OP post I think the option 2 is the right way.