Just popping the paragraph we're arguing over here first for ease of reference. Though it's quoting Stripes, not LF, so not sure it's exact.
"The Respondent must obtain and is currently seeking employment. Once the Respondent is employed full time for over 30 days, she shall provide the Applicant of her income, and the child support will be modified using the offset method".
So this clearly indicates that the judge expected LFEx to be employed soon. The judge also made it possible for the switch to offset to happen soon afterwards, instead of being delayed until annual income disclosure and CS adjustment. Clearly, the expectation was for her to become employed and for CS to promptly switch to offset.
The material change in circumstance is that LFEx has not become employed as anticipated. She is a highly employable individual who is unlikely to be able to prove that she could not find a job of any sort. LF paying full table CS in a 50-50 custody situation is unsustainable, and was clearly never intended to be sustained. But as long as her income being zero means he has to pay more, she has no incentive to do what she said she would do - find a job.
LF needs to ask that A, an income be imputed to her, of roughly what someone of her education and skills could earn, or in the alternative, minimum wage, and B, CS switch to offset immediately, reflecting either her imputed income, or her actual income, should she find a job that pays more.
Forget all the other details about supporting another child, or undue hardship. Don't muddy the issue.
My sense is that it would be better to do it in steps - first, seek to have a "sunset clause" in the order saying that CS switches to offset on (say) January 1 2017. Then if Mom is still unemployed/underemployed (or hasn't provided income information for offset calculations), pursue the income imputation route. I would offer a few months advance notice for Mom to anticipate the change and prepare for it. This makes Dad seem reasonable, rather than just changing his mind about a final order he signed not too long ago.
I wouldn't expect any judge to order Mom to have a full-time job - this would entail ordering someone to hire her full time, which is beyond the power of a judge. But setting a date for a switch to offset is something that could reasonably be done.
Just switching to offset does LF no good; his CS would still be full table because hers is zero. He NEEDS the imputation of income to her as well. By the time a motion is heard, wouldn't it likely be past January anyway?
LFEx is clearly treating his CS money beyond the offset amount like spousal support, not to mention the welfare, so she does not have to work. That is not the intention of CS. Nor welfare, for that matter, but it's not relevant to his motion.
You got your agreement in February or so? So you're at about the six month mark where it is suitable that you bring a motion?
Do you have a mediation clause in your agreement? Don't forget to approach your ex with an offer to settle before bringing her to court. Offer her imputation at minimum wage. If she takes it, her free money drops, giving her more incentive to actually find a good job, hopefully one better than minimum wage.