If he's not sending texts without a response, it's really simple. You just don't respond when you don't want to.
I don't understand the wallflower-wimpy attitude many folks have that they MUST respond to a text right away and are required to answer their phone when it rings. You have more right to your life than any other person does, so take ownership!
The guy has done nothing wrong - he has merely continued to text when you responded to him. I would not be having a conversation with him about too much texting until/unless he texts more than you. For now, you are every bit as much to blame.