*** NOT A LAWYER ***
Whatever support you give her should be specifically classified as alimony and as child support, in a notarized agreement. If possible, it would probably be best for her to not move out until the agreement is in place.
The child support portion is easy, since the calculator is available. Since she’s planning to be voluntarily underemployed, she should probably have a reasonable income imputed for full time work based on her master’s degree. Your student loans and other expenses don’t count here, only expenses relating to the children such as what each of you pays for day care, health insurance, and so on.
The alimony portion is harder, because there’s no hard guidelines. But you can read North Carolina’s laws on postseparation support and alimony (the difference between the two, as far as I can tell, is that postseparation support is temporary while the divorce or alimony case is pending, and then alimony takes over once the divorce is final or an actual alimony order is issued by the court). Unless she cheated (and you didn’t), she’s probably entitled to some support since she was a stay-at-home mom. Again, her earning capacity is supposed to be taken into account when determining the amount, and a larger support (a lump sum, or a few months monthly) should probably be considered to give her time to find a job.
Something else to note, you don’t want to try to trade off less child support for more alimony, because she could just go back to court and seek that the child support be brought up due to the lower amount not meeting the needs of the children. And you probably don’t want to trade more child support for less alimony, both because alimony is tax deductible to you while child support isn’t and because it’s probably easier to have alimony modified than child support (unless you word the agreement poorly).
Also, BTW, you should really look at your bills and figure out what you can do without. Plenty of people made do on much less than $75K.