It sounds like you think that if you had $73,800 (or less) in taxable income, then you could add on an unlimited amount of long term capital gains and pay no tax, whereas if you had $73,801 in income then all your long term capital gains would be taxed at 15%. This is incorrect.
The qualified dividends & long term capital gains are effectively added on top of your regular income. The portion that is in the 10/15% regular income bracket is taxed at 0%. So let's say you and your spouse end up with $50k regular income (ignoring deductions and such for now). You could claim $23,800 in long term capital gains and pay no taxes on it. If you claimed $30,000 in long term capital gains, still only $23,800 would be taxed at 0% - the remainder of $6,200 would be taxed at 15%, since that portion is now in the 25% regular income bracket.
Even if you had no regular income, you could only get $73,800 in long term capital gains tax free - anything above that would be taxed at 15% (again ignoring deductions). So if you have a lot of stocks you want to sell and not pay any long term cap gains taxes, you might want to spread the selling over a few years.
Some things that might help:
More examples and definitions:
https://www.wellsfargoadvisors.com/market-economy/financial-articles/investing/dividend-income-tax.htmTurboTax quick calculator:
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/But before you make any rash decisions from a forum posting or Internet calculator (like sell all of your stocks thinking the gains will be tax free), you should probably consult a tax professional.