Sorry if this is obvious, you may also want to add security to your parlors to increase the amount of defense you have. These can be bought using the money you make in the game (i.e. not Candy Coins) from the Gun Shop. Agent Smith seems to e the best they have, but they also cost a bunch.
Also, if you do the daily draw at the museum, you can eventually get enough dust->items to assemble a cloak of invisibility which when worn will protect all your parlors for 14 days.
But I guess the long term solution is to get higher Fighting stats, and a better weapon. Note, that as most things in the game the fights and battles happen within you "bracket" which is a span of 8 to 10 or so levels. You may want to slow down the leveling up so that this Cooker guy eventually out-grows you and can't pick on you anymore.
In the mean time, collect the money from your parlors frequently so there is nothing of value there for him to steal :-)