The US citizen spouse can begin by filing the I130 abroad.

No this should not present any issues.

Contact USCIS to inquire about current processing.

Not necessarily. Contact the service center for guidance.

You can use the Avvo search tool for assistance finding an attorney.

Yes it is relevant to the DS application.

It is best for you to work with an attorney for guidance given nature of case.

Yes the petitioner must still submit the I864 despite using a cosignor.

You must disclose your full marital history.

No this does not appear the case for you.