Yes, exemptions are 0 now. That was part of the tax reform changes.
Line 17 on Form 8379 refers to credits. Credits will include both line 12 and line 17 on Form 1040, except for the Earned Income Credit that is a part of line 17a if applicable. You may need to look at Schedule 3 of Form 1040 to see more detail about the credits shown on line 12 if there is an 'x' in the box on line 12b.
Line 20 on Form 8379 refers to payments. Payments will include the amount on line 17 of Form 1040 that is reported on Schedule 5 of Form 1040. The most common payment would be if estimated payments were made for the tax year.
