As far as what to tell your W.....if it wasn't for already agreeing to the amount you would, then I would say to not give anything that was not considered for the children. Forgive me if you said, but I don't have your thread pulled up right now, so I can't remember......are the two of you sharing equal time with the children or what? Is she buying their things with what you send or are you purchasing what they need? The down side to this is that it might appear like you are trying to go back on what you originally told her. What was her reaction when you told her how much you would send her?
How do you think she would react if you talked to her and told her your problem with income? Since she makes more than you, she surly knows it is a struggle, however, depending on how mad she is toward you or what her lawyer tells her, is the way she'll go.
If she really doesn't "need" your financial help, then I don't think it would benefit the M, or postpone the D, by you stopping the financial help. I think that is what you were originally asking me (lol), sorry, I get side-tracked. In other words, if you are wanting her to feel the crunch or how things would be after a D, I am not sure this is the way to do it. Would have been if you hadn't agreed to do it.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!
