Best to have an attorney review. If the case is ultimately dismissed, it should not impact your case.

At least 50% of his time in the last five years.

The lack of employment should not present an issue.

This is unlikely if no adoption decree exists.

You can notify USCIS of the change of his status once becoming USC.

You do need the certified copies of dockets to present for interview.

Your status would not expire even if GC is expired.

It appears that your card was mailed to you. Contact USCIS to confirm.

The case would need to be transferred to a waiver of the joint filing requirement.

A short statement should be sufficient.