You might want a HM slave like Linoone or something so you can free up move spots on your other pokemon. Bulk up would be a better move in place of cut for your Blaziken and I know it helps a lot because I own one myself.
Go into the left room, step on a tile, then come back out. The rooms alternate between each other so if you step on a tile in the left you'll get teleported to the right.
Told you you had to be on the top floor. Glad you found it anyways.
Once you find the grave you have to goto the top floor in the wall then push the stone down onto the immovable rubble which will crush it allowing you to push the stone away and enter.