You have to add details of both petitions. Its advisable to seek professional assistance when one is unsure.

Your parents petitions and your brother's petition are separate categories. He will not be immigrating with the parents.

Your anxiety is understandable. But if your visa valid and your employment is ongoing, then you should be fine.

Your I-94 was updated based on your visa. Please seek a consultation to discuss the finer details of your situation.

The DS-160 confirmation number is linked to your fee payment. You will have to submit a new DS-160 for your dependent and pay the fees again.

You do not need a new F-1 visa to re-enter if the existing visa is valid. The advance parole is to keep your adjustment of status application alive...