C'mon. Salesman are notoriously "loose". And you hired him, which say to me you are extraordinarily "tight". Felix & Oscar.
Put him in a box where you maximize his talents, and minimize the damage. Sounds to me like you feel like he owes you something intangible. Maybe he is supposed to act like a better "son" ?
Find a good counselor, set-up 3 or so meetings and have an open conversation about what's going on. What you've been doing to this point obviously isn't working (cause here you are), and it's also pretty obvious that if "something" doesn't happen, this mutually beneficial relationship is going to explode.
And your long-term success depends upon your ability to differentiate between profitable and unprofitable relationships, terminate the unprofitable ones and maintain the good ones. This one is a good one, so your challenge is to fix what is broken in order to sustain it for as long as possible.