I've been through this, but in Canada, so a lot of it is different, but most rules still apply.
Custody works like this - if you live close enough to each other, and in the same school district, then you want shared custody either on a weekly, or a bi-weekly schedule - this way you have equal time with the kids - only one ADDRESS will be named for Primary which is often with the Mother but I do know Fathers that are listed as Primary.
I have no idea where you live, so I wouldn't be able to tell you anything about the numbers, but it works like this in a shared custody arrangement (at least out here & many other places)
Lets say you earn $30,000 and she earns $20,000, and you have 2 kids - First you calculate what you would pay her based on $30,000 and her having the kids full time, then you calculate what she would pay you based on $20,000 if you had the kids full time - your amount minus her amount equals what you would pay her (or vice versa if she makes more than you).
If she doesn't work, that can make things more difficult because then you could also be responsible for alimony.
If it's available to you, and you know that the default amount will break the bank, then file for undue hardship.
In all honesty, no-one actually needs to courts to decide on custody or support arrangements if parents can work together for the best of the kids, but unfortunately it's quite often that parents use the kids as some form of leverage in one way or another.
Make sure you request that she is not permitted to speak ill of you to the kids, or with the kids around to hear it (and you agree to the same), and be very detailed in any sort of arrangements for holidays, time from school, doctor appointments, dental, everything related to making decisions for the kids.
If you cannot agree with each other about things regarding the kids, judges are less likely to rule towards a shared custody arrangement, so whatever you do, bite your tongue, avoid mud-slinging, and if she is as you have stated in your posts, she may very well sink her own ship if she cannot keep her mouth shut.