I would start all over, prepare a joint 1040, mark it "SUPERSEDING RETURN" and paper file before July 15.  99% of the time, Form 1040-X is the best choice, but not this time.  If you use a 1040-X, I think you have to attach a 1040 anyway to show how you came up with the numbers.  Has a refund been paid already on the original, incorrect return?  The superseding return may show a refund in a smaller amount, but IRS will adjust the account and send a bill for the difference.  Or if the refund is higher, they will pay only the difference (with interest).