“ he is in the military (CA resident, stationed in VA) and is not required to file a CA state return.’--> I guess your husband doesn’t need to file his VA return but he, as a full year resident of CA, needs to file his CA return.
“ However, I am a VA resident and need to calculate a married filing separate federal return to do my state return.”---> As your spouse is a full year CA resident( though he stationed in VA), you can file MFS on your VA return and federal return.
“How much of the itemized deductions (mortgage interest/real estate taxes) can I take since my husband is not required to file a state return. Although we have a joint account, mortgage payments/real estate taxes are paid out of his account and the 1098 is in his name.”---> You are unable to deduct the mortgage interest and r/e taxes on 1040 Sch A if you pay for your husband UNLESS you are legally liable for paying it. You have to be legally liable for the loan in other words.What I mean is that if you are the primary borrower, you are legally obligated to pay the debt and you actually make the payments. If you are married and both you and your spouse sign for the loan, then both of you are primary borrowers. If you pay your mother’s mortgage to help her out, however, you cannot deduct the interest unless you co-signed the loan.