Conceptually great idea, but I think setting the cap of top employee compensation as a multiplier of the lowest paid employee is a better start, as well as requiring full benefits for any employee rather than a minimum. (You will have to tweak other things, and make sure to crack down on wage theft for overtime, etc, but this will remove the disincentive to hiring full time.)

It isn't so much that we want to discourage investment in food supply and other service sectors but rather to increase the living conditions of those working in them.

It will mean increased labor costs, decreased stock market profits, and a bit of inflation. I argue that for humane labor practices, this is an acceptable compromise for a civilized society.