Red Sea just got back to me. They said it's unpredictable with that variance in the level as is and it's too much, so they would recommend to fix it. They said it was typical practice (as did multiple YouTube videos including BRSTV) to level it, fill it, measure the level again fully filled and then if it isn't level, take out 3/4 of the water into a storage container, level it again and fill it again. They said this is a very typical process and not unusual to have to do. I guess lucky for me that the tank has new uncycled water and nothing else in it. Hopefully I can get some shims under the current shims to prop the front up enough. Thanks for everyone's help/input!