Apparently the checksum is the last 4 bytes calculated by the entire file except the checksum bytes with crc32. I haven't tested it, always back up your save. If you can hex edit and find your name you can change it and apply the new checksum. Good luck.
Can you help? I'd be willing to put out a save editor if two things were provided. (1) A list of hex values along with what item they represent. (2) An address map of the save file, whatever values you want changed with the address in the save file.
Reason being, I don't have this game and wouldn't be able to save hack myself.