I'm not convinced about #2 and #3 above.
@mj6974 the answer is simply this: If you can not e-file because the father e-filed first and you are getting a block on the child's SSN, simply print the return and file by mail. You will get the refund in 4-6 weeks instead of 2 weeks, but it will still come. Then, a few months later, the IRS will send letters to both parents to investigate the duplicate dependent claim. You will respond with the information that the child lives with you, and offer to provide proof.
You should plan to gather that proof now -- could be things like emails and text messages documenting visitation, a letter from the school documenting where the bus picks up and drops off your child, photos of family events, or any other proof that will show the child lives with you.
Note that the IRS will not care that the other parent does not pay support, that's not part of the IRS rules or formula for deciding who is allowed to claim the exemption. The key rule is, the exemption goes to the parent where the child lives the most. So be ready with proof.
If you did not claim the exemption in past years because of this same issue, you can amend your tax return to claim the exemption and extra refund, and the IRS will launch the same investigative process for those prior years. You can go back as far as the 2012 tax year (which was filed in early 2013).
