No, you cannot be issued an H4 if you are no longer married to an H1b.

The issue is not the warrant, it's the DWI. It makes you inadmissible until you can prove you are not an alcoholic. Meanwhile find a criminal...

Yes, you can request CIS to connect your I-360 to your pending I-485 and you can continue to file for work permits based on the 485.

Notify CIS to recapture the priority date so they will process the adjustment application.

If you naturalize, they will be automatically derivative citizens. They can apply then for US passports and for certificates of citizenship.

You do not need, and cannot have two work permits.

Same as the 751, as you said, but updated. Bring originals of everything to the interview.

You can file for all of them. If and when your parents get green cards they also can file for your sister.

You need the visa, and a current letter of employment.

One would have to review the prior denial very carefully. If the employer is not willing to help. there are any number of things that could go wrong.