I agree with muzza, leave out the parts that are emotional, state only facts and what you intend to do. It's terse enough without those statements. I'd state it this way:

"Perhaps you think I won't go to too much trouble over a mere $60. Frankly, it's no longer about the money. It is about the lack of respect you have shown me, and when you treat me that way you will find out that I do not back down."

Of course if you've already sent it, that's fine. I can't believe he used his business as point of contact then pulled this crap. Going after his business is the smart thing and that should jolt him into reality.