Nice work, Sam!
I noticed that you used a 0001001 formula for "commemorated by priests." This is slightly problematic for me because the second syllable of "commemorated" (which receives the primary accent) is assigned a 0, while the fourth syllable (which receives the secondary accent) is assigned a 1. So ideally, I would prefer to use a 0101001 formula for this phrase.
I also noticed that you have divided the last sentence between "And boasting, we say: Our Father" and "which art in the Heavens." In this case "Our Father" is not grammatically related to "And boasting, we say," yet they are grouped together. Also, "Our Father" and "which art in the Heavens" are grammatically related, but they are not grouped together. I believe that a better choice would be to divide the sentence as follows: "And boasting, we say: / Our Father, which art in the Heavens." And in general, phrases should be broken after periods, semicolons, and colons whenever possible.
Your solution for "Heavens" isn't such a bad idea, but I am uncomfortable with the transition to the diatonic scale on the "ni" immediately following it. I don't recall ever hearing a transition like that before, and I'm not sure that it's traditional. I think it is an "unwritten rule" that melodies only move from high "pa" to either "dhi" or "ke" in Plagal Second Mode. Perhaps Papa Ephraim can either confirm or refute this intuition of mine. I think that a more traditional choice in this case would be a cadence on "ke" for "which art in the Heavens." We have enough choices in the formula book that we can still hit high "pa" for "Heaven" and end on "ke." From "ke," we can safely transition to the diatonic scale for the next phrase on "dhi" ("hallowed be Thy Name").
We could implement these two suggestions as follows: Use an heirmologic bridge of "pa dhi ga dhi" for "And boasting there-" followed by the fourth 100 formula on page 557 for "-in we say." Then use the end of the 0010 formula on page 576 for "Our Father," a "ke" for "which," and then the last 10010 on page 577 for "art in the Heavens." Then I would put a petaste with a klasma and a fthora for "Hal-" and use the end of the 10X0100 formula on page 560 for "-lowed be Thy Name."