Around here, whoever has the best and cheapest insurance provides coverage and the other pays part - so not just the NCP. So when DH went back to court because BM wanted more CS, both of them had to put what they would pay for a family plan through their employer. 

So my guess is that BM should put what it would cost her to insure SS and DH should put what it costs him.

Here is the calculator if the non custodial parent provides health insurance they get a credit, if they don't their "portion" is included in the ordered amount. Your husband doesn't need a lawyer to file for child support he can submit the forms himself to them. Their percentages are pretty cut and dry. 
 

https://csapps.oag.texas.gov/monthly-child-support-calculator

We are an income shares state so whoever covers medical is credited that amount.

Ex. Total income available = $10,000/mo.  

$6,000 of that comes from dad $4,000 from mom.  Dad is responsible for 60% and mom 40%.  Split is 50/50 so there are no offsets for difference in overnights.

Dad covers insurance at $100/mo. while his share is only $60. So he gets a $40 offset each month.

If mom were to cover at $120/mo. her share would be $48 meaning dad would have an additional $72 added to his monthly obligation.

In our case, both parents have coverage that is within guidelines but SOs is much better so he covers it and has a monthly offset. 

BM is also responsible for the first ~$800 out of pocket on medical expenses (2 kids) before their income split takes effect on any other ordinary medical expenses.  That additional responsibility falls to the payee regardless of CP vs NCP designation.

Just looking at the TX calculator it would appear that covering medical/dental is just a reduction in net income before they calculate the flat percentage. 

I would assume (and possibly incorrectly based on the way its worded) that she would only include that dollar amount if she were actually going to provide medical/dental coverage for the kids.