For Book of Mormon, 1 is Rory O'Malley and 2 is Kevin Duda. Pippin, 7 is Andrew Fitch, 6 is Andrew Cekala, 5 is Orion Griffiths, 4 is Bethany Moore, and 1 is Rachel Bay Jones. 2, 3 and 8, I have no clue. Sorry!
Re Newsies #8- based on the cast list, I'd bet it is Julian DeGuzman. I know it is not Julie Foldesi, John Brady, or John Dosset, and if the other signature is John Michael Fiumara, that only leaves Julian with a name starting with the letter "J"