I'm sorry but the only suggestion I have for you is to come up with a budget that doesn't include support payments -- they obviously are not going to be reliable. I definitely would NOT let him off the hook and allow him to "spread the payments" out over 3 months. He'll do that or not....as
he pleases anyway!
Beyond that, keep good records and
stay strong with your boundaries.
Not what you wanted to hear, I'm sure.