I would create some fixtures like korbels that are about 4 inches thick. You could either create the angle of the French cleat directly in the korbel or attach the French cleat o the front of the korbel. Either way you would have the French cleat standing proud of the walk and the vertical height of the korbel would negate any levered force you are worried about. And toy could design the korbels to look like wall decor when the table is not hung.