The good news is that you have more than three months to work on this problem.  The income should be reported on a Form 1041, but claiming credit for the withholding may be a problem.  Try requesting it from the payors, along with a corrected 1099R and new 1099-Misc, but don't expect them to be helpful.  You can refer to the lack of cooperation, though, in an attachment to the 1041 claiming the "withholding in respect of a decedent" (term I made up) along with the income in respect of a decedent.  The worst IRS can do is disallow it and tell you how they think it should be done.