@djtsukasa I do not see anything in the publication that provides for DoD employees assigned outside the US. If you are in the military and receiving non-taxable combat pay that can be added back in the determine the credit, but that is it.
Also, amounts excluded as foreign earned income (including any housing exclusion) on Form 2555, line 43 are not eligible for consideration for this credit. Is that where your spouse's income is listed? And if so, she would not be showing any "earned income" and therefore it would not appear there is eligibility for the credit.
Since your original question was how to separate your income from hers' on the tax return, that is actually quite simple but won't meet your objective. You could file MFS. But taxpayers who file MFS are not eligible for the credit. So it is a catch-22.
https://www.irs.gov/pub/irs-pdf/p503.pdf
