Welcome to the forum. I agree that some more exercise might help. Also, in my experience labs are very smart and if they benefit once from achieving something then watch out. I would recommend getting some kiddy locks for the cabinets before he gets into something harmful. You could also try double gating (vertical or horizontal) the area he should be in.
"Never doubt that a small, group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has." - Margaret Mead