It is a possibility. But I do think that at this point, he is trying to be spiteful and make you mad. I think that when you first broke up, he may have hoped that you would have came back to him. However, as time went on and you moved on without him, he may have realized that you coming back may not happen. As a result, he seems to be finding things to do to upset you, get to you, and make you mad. The reason for this, is because he is mad and upset and he would like you to feel the same way that he feels.
On some level, he may be hoping that you realize that you made a mistake not being with him, his way of showing you this is not paying the child support. He may hope that you will come to see that you need him in some way (even his money), and that you leaving him was a mistake.
I do think that it is the same thing. For many men in my experience. They think you would beg for them back, or least not be so "nice " about them leaving. And now that you moved on and did something better with yourself. When people in general break up with one another. The last thing they want is to see that person doing better without them.
Since you are doing better without him, he may now see what he has left behind, and that he has no chance of getting you back. Even though he left, somewhere in the back of his mind he may have hoped you would beg for him back, or still be his "friend with benefits" but since you did the strong and mature thing, it makes him mad and spiteful. I think this is what affects him the most. Now he tries to find ways to get back at you, for doing better without him.