Ok... I've filled out Form 8958, allocating the income & withholding pieces to each spouse on both their MFS returns, but it has no impact on the income/withholdings that show on the face of the 1040. Wages & taxes are showing as they were reported/entered on the W-2, NOT by how they're allocated on Form 8958.

Is there a toggle to activate Form 8958? Do I have to adjust the W-2's to correctly allocate the 50% to each spouse?