Have you set expectations yet? I think you need to first discuss why he isn't pulling his weight, and tell your partner that if things don't change, then you are going to have to figure out how to continue the business without him. First tell him what you expect, and if he doesn't agree and you can't come to a compromise, then give an ultimatum.

At this point, it probably doesn't make sense to get in a legal fight. I think worst case scenario is you break off and continue on your own, and jettison the minimal contribution your partner has made to the project. It doesn't sound like the business is at the point where he is going to lawyer up and sue you. It would cost you both more than its worth at this stage.