Reused text adaptation by Sandhofe, but added Alleluia at the end (standard formula for antiphons) for lack of a better solution.

Not sure what you think of the 1930 nocturnale of St. Peter's basilica. They seem to have adapted the melody of "Surrexit Dominus vere, alleluia" https://gregobase.selapa.net/chant.php?id=18575

An older example of using the mode VI Easter invitatory model for this text https://www.google.cz/books/edition/PSALTERIO_ANTIPHONALE_ROMANUM_DE_TEMPORE/chZkAAAAcAAJ?hl=en&gbpv=1&pg=PA216&printsec=frontcover

A different melody, 17th c. Polish print http://polona.pl/item-view/fac864dd-3ca2-4d3f-a488-d75eddfbc9df/0/30324aec-10a1-4c92-ab36-c8b35277c0f7

Excellent point. Not knowing these precedents existed, I had chosen to stray from the mode 6 Easter inv. melody because I find it a bit tiring to have the same ps94 tone every day in Eastertide even on feasts. But since there is precedent, I will go with the precedent.

Following precedent, reused the I/ for Apostles in Eastertide, replacing "Regem Apostolorum Dominum" with "Christum Regem crucifixum", following the 1930 Nocturnale of St. Peters basilica

Re- (regem) is not a salicus, but a neumatic break (vi-pe), as it appears in the I/ Surrexit