1) You can request your tax transcripts from the IRS. Call them at 1-800-829-1040 or use IRS Form 4506t

2) I would suggest married filing separately

3) The parent who had the child for most of the year should claim him/her. Be prepared to have to prove this though if you take the benefits since she seems to be a little angry and vengeful. Does one person officially have court ordered custody? In separations where there is not court documents saying who cares for the child, the IRS goes by who had the child for most of the year.