If you file as married filing separately, and one spouse itemizes, both spouses must itemize. You can't use the standard deduction, even if your itemized deductions are zero and you pay higher taxes because of it. The two spouses can divide their itemized deductions any way they like; although 50/50 is the most common recommendation, the IRS will not object if you divide them a different way, provided they were paid from your common funds. (In a community property state, you must split income and deductions 50/50.)
