Yes, a decision on your i-140 could lead to a quicker decision on your I-485.

No, a step child must have been under 18 at the time of marriage.

Anything is possible. Normally, if a person is eligible for adjustment of status, they are approved.

Generally there is no requirement to file an I-140 to be eligible for an h1b But sometimes, such as a post sixth year extension, there may need to...

Working as an independent contractor [thereby getting a 1099 instead of a W-2], without USCIS authorization, is unauthorized employment.

It should have no impact on a person's immigration status which EAD they present to which employer.

I expect the pending charges will cause delays in getting a K1 approved.

Provide the information and she should get the later expiration date.

Anything is possible. Perhaps you should try to correct it.

The sixty day grace period does cover this gap.