Taxes owed increased after entering 1098-T

The first step is to go over all your entries to make sure they are correct. If you don't find an error, delete the form. Print a copy of your forms and then go back and re-enter the 1098. If this is still happening, examine both the before and after versions to see where the difference is coming from.

Here's the general procedure for viewing the forms list and deleting unwanted forms, schedules, and worksheets in TurboTax Online:

1. Open or continue your return in TurboTax.
2. In the left menu, select Tax Tools and then Tools.
3. In the pop-up window Tool Center, choose Delete a form.
4. Select Delete next to the form/schedule/worksheet in the list and follow the instructions

Since he is over 18 and not a full time student, he can only be your dependent if he has less than $4300 of income for 2021. 

See full dependent rules at: https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html

He must be half time, or more, for you to claim the most generous tuition credit, the American Opportunity Credit