Will a shop lifting arrest affect my friends citizenship application? He was arrested when he was 17

Most likely not, but it must be disclosed on the N-400

False allegations by abusing violent husband

She should get a family law attorney, preferably one that understands immigration.

USC applying for stepmother?

Yes, but not before you are 21

And your question is?

USC applying for children

You will need to petition them. They would only have become US citizens, if they already had the green cards when you became a citizen.

Renewing Green card?

The fact that you may have paid a lawyer really does not mean anything, if the arrest warrant is still out there.

Travel on B1 Visa to USA while H1B is under processing

As long as you can demonstrate that you will be returning abroad, there should not be any issues.

I am a US Citizen and I got married in Mexico to a mexican citizen. My husband lives in Mexico. Is my marriage valid in the US?

If your marriage is legal in Mexico, it is legal in the US. The title company is correct.

Whats the best thing to do in my current situation with the divorce and immigration issues?

He cannot do anything against you. You really should be discussing this with your lawyer. That is why you have him/her. She/he knows all the facts...

M2 Visa to H1B Status

This is where the last action rule would apply. Your wife's status would be determined by the last action USCIS takes.