Re Lil I believe their original decree stated that the child support would be a percent of his net income........He made the May and June payments from his unemployment check, and the amount he paid was the original percent, but of the unemployment check. Looks like you have enough information and I do hope your bf borrows the money from his mother to move on with this situation.
What he should have done is right then sat down with her or communicated with her and said, this is my new financial situation, let's renegotiate. But at the time, his priority was getting over the quad bypass surgery, dealing with the layoff and cessation of income (except for umemp), stopping drinking, etc Those "are" a lot of issues to work on all at once.
And somehow I think he thought she should have been able to intuit what he was going through and be sympathetic and understanding without his having to ask for it. True to a point but with much anger, if she is still or ever was angry, maybe sympathy goes out the door. Especially if she feels she was the wronged spouse.
This would be a lot to ask from anyone, but it makes no sense to expect understanding from her, given their history, and given his knowledge of her personality (he's known her since she was 15.) Lil, those early loves hold some people captive for an entire lifetime even when intellectually one or both know it was not a good or mature/compatible R.