@jpinfant
I added some additional info to my answer above and edited it for clarity (hopefully). So you may have gotten additional emails with revised material as I worked on it. Sorry if I've caused any confusion. Please return to the forum to see the full final answer.
The important step to make sure TurboTax includes the $300 in cash contributions is to officially conclude the deductions section as I outlined above, then once TurboTax knows that you are definitely using the standard deduction, the next screen should ask you about the $300 in cash charitable donations. I don't know if you went far enough to see that screen or not. It might also pick it up in the Federal Review, but I don't have a way to test it.
Check the Form 1040, Line 10b to be sure it's showing up on your return. We can tell you how.
