Do you know if USCIS has announced that the cap for 2016 on U visas have been reached?

I agree with my colleagues. Review www.uscis.gov.

How to obtain interim EAD while application in process.

I agree with my colleague. Contact a US immigration attorney to file a follow-up with USCIS.

Is there any expedited processing service? Thanks

There is no expedite for PERM. Once you are filing the i140, there are premium processing methods.

Contact your company's US immigration attorney for review before you leave the US.

File the AR-11 online and schedule an INFOPASS with the local office to see how they wish to handle the move. Contact a US immigration attorney...

I agree with my colleagues. Answer all questions truthfully and contact a US immigration attorney prior to filing.

Now the work permit has arrived. Should I use it to apply for SSN or ignore it to not notify the USCIS one more time ?

This is not a clear question. Listen to the attorneys that you have spoke to about the consequences of your filing and your disappearing aunt.

Currently on H1B with visa stamp expired. Will use AVR to return from Mexico to USA. Changing jobs so which I-797 I should use?

Contact your company's US immigration attorney before you leave the US.

Where should I go initially to get the sponsor?

I agree with my colleagues. Find a US employer willing to sponsor you for an employment-based status (generally H1B). Contact that school's US...

Can my husband ask for a pardon since he already has 5 years and we have two daughters born in the US and he has two older ones

I agree with my colleagues. Contact a US immigration attorney to review the specific immigration history and determine waiver eligibility (if any).