The Book: "Sefer: Minhag Tov" which seems to have been written in the year (about) 1273-1275;(maybe as late as 1300?), has a list of Jewish customs. One of them (#36), states:
"And it is a good custom on Friday nights, when we come (home) from the Synagogue, to go right away next to the candles lit for the honor of the Sabbath, which we made the blessing upon, and stand next to both of them and say: "Oh angels of mercy and peace, May your coming be for peace, May your coming be for peace, Upon you should be peace, For all of you there should be peace..." And so too have I found written that Rabbi Aharon of Regensburg acustomed himself to do so."
"Sefaria.org" writes the following information about this Book, showing the author is assumed to be an Italian Rabbi of the middle ages:
"Sefer Minhag Tov, an anonymous treatise composed circa 1275, whose author may have studied with northern French Tosafists but who certainly did study with R. Moses ben Meir of Ferrera and perhaps settled in Bari or Taranto..." From Kabbalah: Journal for the Study of Jewish Mystical Texts, Volume 6 pg. 144 (Courtesy of R. Joel Zeff)."
It therefore seems that the original words of at least a proto-Shalom Aleychem liturgy was already in use as early as the mid thirteenth or even twelfth century and probably has roots beforehand as well.
Therefore it would seem to be an error to attribute the creation of the liturgy to Solomon Molcho, or any Jewish figure who lived and was active in the early 1500's.
Here is the link to Sefer Minhag Tov:
https://hebrewbooks.org/pdfpager.aspx?req=8903&st=&pgnum=12&hilite=