Scandium: The only exceptions to the six month rule is birth or death. You've always been able to claim a child in the year of their birth, even if there's less than six months left. Happy amending! ;)
Ugh. Well nobody told me that.. I only saw the 6 month rule, not the teeny-tiny text with the exception. Taxact will charge $14 to open my return again, and it's not clear that will even calculate the new values for the 1040X. Started filling out by hand (well by PDF). I'd reduce my tax by 25% of the deduction, but it would lower my foreign tax credit by 17% off it, or something like. Maybe I'd get $400 back? Not certain though. I'm not sure I want to bother, seems like a giant PIA. (having income in two countries I had a 30+ page return)
edit: looks like a $14 fee will let me open and update my return with taxact. Since all the calcs will be done automatically (I could not get my "tax owed" to be the same when doing it by hand) it might be worth it for a potential $400+ payout.