I can't finalize because it says "Charitable contributions has an unacceptable value"

Turbotax does not do a great job at handling the special $300 charity deduction for taxpayers who take the standard deduction.  It asks about the special $300 deduction at the end of the "Deductions and Credits" interview, just before the Review.  If you enter itemized deductions in the usual place, and also enter the special deduction, the program will complain.

If you are taking the standard deduction, go back into the "Charity donations" section on the Deductions and Credits page and delete your charity donations listed there, and only list your special $300 deduction during the Review.  If you are itemizing your deductions, go to the Deductions and Credits page and click "done" to trigger the review step, and zero out your special deduction.