That is great that you have used the TurboTax Withholding Estimator Tool as it will give you the most accurate amounts for your desired resolution when it comes to tax liability at the end of the year. If your happy with the amount determined using your first job for your withholdings in calculating your overall tax liability for the year, you can use option 2(b) on the w-4 for your main job. By using the table this will account for both jobs. For the summer job's w-4 you should enter EXEMPT on line 4c.
I you took off the dependents on the w4 estimator and nothing changed, your correct this usually means your still in the same tax bracket. So weather or not you add in the deduction you would get for your dependents it still leaves you in the same bracket. Example: Income is 50,000 for MFJ, you have a standard deduction of 29,200 and 2 dependents under 17. This equates to 50,000-29,200=20,800 now subtract the possible 2,000 per dependent under 17 (the income is below the phaseout for this credit) 20,800-4,000=16,800 If there are no other deductions or credits then you end up with taxable income of 16,800 which leaves you in the 10% tax bracket. You add back in the amount taken out for the dependents and you are still in the 10% tax bracket. https://www.irs.gov/newsroom/irs-provides-tax-inflation-adjustments-for-tax-year-2024
If your husbands job will be variable income then yes it is best to check the withholdings and make adjustments every few months as the income changes. Best way to do this will be using the Estimator tool and his last pay stub. You would adjust the W4 by adding an additional amount if needed. The estimator tool will show you what to add to the W4.
