You have not given the information needed to answer your question. The tax rate on long-term capital gain depends on your filing status, and on taxable income, not net income or AGI. Taxable income is AGI minus deductions. We would also need to know how much of your taxable income is ordinary income, how much is qualified dividends, and how much is long-term capital gain.
Finally, the question is not how much stock you can sell, but how much long-term capital gain you can have on the sales. The total proceeds of the sales don't matter. What matters is the amount of gain.
