You certainly have a good claim to half of the rent, if you both signed the lease and the other did not move in. However, you would have an obligation to mitigate your damages by trying to find a replacement roommate.
It is not as clear about collecting for utilities, as the other is not using any of the utilities. Perhaps you could make a claim for half of the base rate for the utilities.
The Harris County Dispute Resolution Center offers mediation services for small claims. This may be a good option for resolving the past debt and setting up a payment plan for monies owed. The result is a legally binding contract that is enforceable in small claims court in the event that the person does not honor the terms.