RFE response dates have been extended due to the pandemic. USCIS will consider a response received within 60 calendar days after the stated due date.

This emphasizes the importance of working with an attorney. The most basic requirement, to become a US Citizen, is the ability to speak English....

You paid a fine at the store? That would not be typical. Did the store file a police report? It does not sound like you were arrested or convicted...

I, too, have found this to be quite inconsistent. Some come very quickly. Others take months.

Lying on your I-485 is immigration fraud. Correct this at the beginning of the interview.

"Does infidelity affect the determination of primary physical custody?" No, not in the slightest.

You should be able to travel, within the US, with a TSA approved document. https://www.tsa.gov/travel/security-screening/identification

You may check processing times at the following link. https://egov.uscis.gov/processing-times/

Unfortunately, a sibling visa takes 15-20 years. Your sister would need to be in status to adjust status.

That fee seems excessive. I suggest that you privately consult with another qualified immigration attorney before making your decision. Good Luck.