If you don't have any contact with your estranged husband, you will probably have to file a separate return (Married, Filing Separately) - answer any questions about his tax situation as best as you can.
When filing Married, Filing Separately, both of you must use the same method of calculating deductions (standard or itemized). Pick the one that works best for you - if there is a conflict, the IRS will follow-up with any questions they have.
You may, however, qualify to file as Head of Household - see Can a married person claim Head of Household filing status? for the requirements.