you can try this: http://www.xpgamesaves.com/topic/112111-madden-15-save-editorchecksum-fixer-xbox-360-mod-tool/ Not sure if it will solve your issues or not. I would still suggest that when you load the game save (with modded XP) that you save it manually before you adjust the attributes of your players. It may help prevent the ethnicity change
Does this work with xkey or just jtag? Also can you use this for online connected careers? Thanks so much for any help.