the credit is limited to your tax liability (before certain credits/additional taxes) . The amount withheld does not matter. selling stocks to generate gains may increase your tax but you would have to do a tax calculation to see how much gain you would need to be realized to increase your tax applicable tax liability to $7,500 or more. depending on your income some long-term capital gains could be taxed at 0% which doesn't help. if there are net short-term capital gains, they are taxed like wages.
here is one tax calculator. there are others. if you use several different ones, you will likely get different results depending on whether they reflect 2023 or 2022 laws.
https://filemytaxesonline.org/calculate-your-tax-refund/
