Note that, due to the multiplying effect of increasing the amount your taxable Social Security income, your marginal federal tax rate at this income level is 1.85 * 15% = 27.75%. You would have to have at least $21,900 more or $18,400 less in non-Social Security income (or an increase of $18,400 in above-the-line deductions) to get back down to a 15% marginal tax rate. (This calculation assumes that you both are age 65 or over. If under, the 27.75% marginal tax rate bubble will shift a bit relative to your AGI.)
