You will pay no taxes on the dividends until you get to the $39,375 point. But, the $39,475 (not 39,375) is taxable income, not AGI. But then you will pay 15% (not 12%, but also not 24%) on QD.
Your AGI includes any qualified dividends (QD). So, in your first example, your AGI is $32000 + $5000 = $37,000. Your taxable income is 37,000 - 12,200 (standard deduction) = $24, 800. None of your QD are taxable (technically taxed at 0%).
Your 2nd example has the same results. QD taxed at 0%.
Let's make a 3rd example. $45,000 salary and $10,000 QD = $55,000 AGI. 55,000-12,200= 42,800 taxable income. 42,800 - 39,475 = $3,325 QD will be taxed at 15%. $6675 QD will be taxed at 0%.
Note that while you are technically "in the 24% tax bracket", none of your income is taxed at 24%, because of the special rate for QD.
