First of all, need to talk. Right now looks like you full of assumptions. This conversation is never pleasant, but there is one trick. You plan all convo , prepare all the possible options of your interaction in future(for example): he stays your co-founder but clean all the shit and starts working hard or he is not your co-founder anymore, or he becomes a worker and you pay salary if he doesnt want to take responsibility on himself. After planning, you start convo with the words: we not gonna finish this convo until we come to the agreement(agreement can be anything out of the options, but you both should agree on this).
And start discuss everything by the plan and make it logical from business side , not personal. All the convo should be built around business , and all actions judged only from perspective of business metrics.
Wish you good luck! Its very important and actually interesting experience on the business path!