The file is full of garbage, no real save data inside.
Besides that the proper size for Gen 3 saves is 128kb. You should check if FlashGBX is able to dump the full 128kb save.
He provided ME3 files for them on his Github https://github.com/notblisy/RUBYSAPPHIREDLC/tree/main/MYSTERY EVENT 3 EVENTS
Use the WC3 Plugin to inject them into your save.