The tune was written by Electric Light Orchestra front-man Jeff Lynne. For evidence, we have the songwriter copyright for BMI, which lists Jeff Lynne as the sole composer. In addition, the extensively researched website JeffLynneSongs.com has the following information about what they call the Concert Coda of "Mr. Blue Sky":
The closing part of the song, ...
This isn't specific to opera. Lyrics we can't understand have a tendency to sound more meaningful and profound to us, because we impose our own sense of meaning on them. We assume that they are the perfect marriage to the music that we imagine them to be. This is true not only of foreign-language lyrics, but also gibberish lyrics, unintelligible lyrics, ...
It seems it might have been Franco Ricciardi, playing two roles (Arturo and Normanno).
In the MYTO 2009 album release back cover it seems to appear his name:
Another reference can be found in esdf-opera.de.
I don't know the top example, but the bottom example is the very famous quartet ("Bella figlia dell'amore") from the third act of Verdi's opera Rigoletto.
This particular performance is a rather...busty one by Pavarotti and Isola Jones. You can enjoy it here.
I just want to note that there is similarities in those two lines to other minstrelsy numbers in terms of context: Oh My Darling Clementine. It is a simple address that fits in the context of the opera as a whole but alone it is rather plain.
The second note is the translation gets rid of several poetic features. Namely the repetition on the second line (...
I think it is a slow played version of Antonio Vivaldi's Dixit Dominus, Juravit Dominus.
Alternative link, even faster.
I've found different paces to play it, and in the movie soundtrack they played it really really slow.
I finally found it, after listening to a lot of arias: the music is taken from "Io son rea dell'onor mio", in Vivaldi's Argippo. This aria was discovered only in 2006, so it was not known at the time of Bezzina's recording.
You may enjoy the arrangements made by the Uri Caine ensemble released on this live CD. They don't fit any of your genre recommendations exactly, but they're interesting arrangements nonetheless.
You can hear the tracks in this YouTube playlist.
Lastly, you may be interested in the term "Wagnerian rock."
@alephzero has provided the relevant links in the comments, and I'm just creating an answer here for completeness.
The cantata Cessate, Omai cessate (RV684) containing Ah Ch'Infelice Sempre isn't the Stabat Mater (RV621). Finding translations of Stabat Mater is easy, there are several here, for instance.
For a translation of Ah Ch'Infelice Sempre, you can ...