A lot of questions. We will do our best to answer them, but we are not acting as your attorney and to be certain of how the rules are applied locally you will need consult with an elder law attorney who practices in your state. To find one near you, go here: https://www.elderlawanswers.com/elder-law-attorneys.
That said, first, your mother cannot transfer the IRA without liquidating it. When she liquidates it, the funds in the IRA will become taxable income to her. Whether she will actually have to pay taxes depends on the amount of the IRA, her other income, and her available deductions. Second, the income should not affect her Medicaid eligibility because while the IRA liquidation is income for tax purposes, it is not income for purposes of Medicaid eligibility. Third, as long as your husband is receiving Social Security Disability Income, he falls within an exception to the usual Medicaid penalty for transferring assets and his mother can transfer her liquidated IRA to him without penalty.
For more information about IRAs and Medicaid, click here.