Bring a third party as interpreter to the interview. If cannot, then follow your lawyer's advice.

I agree. Don't think parents will be issued visas to travel to the US at this time.

Can I do two jobs with EAD (765)?

Concurrent jobs is allowed under H-1B.

Citizenship to illegal immigrants ?

Don't be under any such illusions. Will never happen.

Do I need to withdraw I-539 application for B2 after the petitioner left the US?

The choice is yours. Not obligated to withdraw.

Incorrect ssn in approved h1b petition?

Complete and total non-issue. Don't worry about it.

Once you are admitted into LPR status, yes.

Reentry to USA with expired TN visa and valid I94?

No worries - you should be readmitted upon return.

You were perfectly in your right to request that refund for transactions prior to your having attained LRP status.

I-140 related question

The 6 months countdown you are alluding to begins on the day the I-140 gets approved.