You're not a "fool" for extending basic human trust to someone. When you're a decent person, you just have a built-in assumption that other people are decent as well.
He is to blame for acting like a pig. He'll have a terrible life because of it.
The relationship's caused some damage to you but he's just a person, and you're stronger and better than he is, because you're decent.
You'll brush this off and get moving. You'll be okay!