You have touched a nerve. First, the part where your developer breaks the site and leaves really tells you that he doesn't care about the product.

On the other hand, the fact that he chooses to leave when his time is out shows you that he values his time. He values it more than the company, if you want to look at it like that.

Not everyone who works for you will love your company. For some people it's just a job. Now, it's your choice to make if that is good enough for you.