My opinion is that from the sound of it....I wouldn't want him to have my dog. He just doesn't sound responsible enough. If he felt "he was in love and HAD to have her" and wasn't so in love a short time later.....then he is an "impulse buyer" and often times those dogs don't stay in that home. Not always of course. It's just "how deep is his love?". I would call it a "learning lesson" and we all go through them. Man, I just went through a HUGE learning lesson
. From now on, the contract should include that payments are to be made in cash and that if a person backs out before the designated payment timeframe expires, then (for example) $300 is nonrefundable. That way the person is going to take it seriously and not go "shopping around" while under a signed contract. In addition, you aren't "totally screwed". Honestly, I'd let this one go.....I have a feeling pushing it would get you less than nowhere.
and P.S. He most certainly should cover the insufficient funds, however, I'm sure he won't. So sorry.