From an input standpoint, there's no option within ProConnect Tax/Lacerte to use the MFS exception on the NC return when federal is filing MFJ.  (For some states, there are options and you'd find them mostly under Misc. Info./Direct Deposit, on the tab for the respective state.)

What you need to do is to prepare the MFJ federal return as usual and code everything correctly for T/S/J, State, and N/S.  Check that you are happy with the federal return in terms of completeness and accuracy. 

I assume you have already considered their matrimonial domicile based on their facts and circumstances (since they're not settling in TX at least for the time being) and how community property rules may apply, if at all.

Review the MFJ/MFS comparison to get an idea how the return would be split.  Then, follow the instructions in this article to split an MFS return for the NC husband:

https://proconnect.intuit.com/support/en-us/help-article/tax-filing-status/generate-married-filing-j...

Hope this helps.