You bet!
Gosh CH – you ask such great questions!
Of course there's the obvious correlation here of Ennis's trespasses (sins) with Jack and his need to be forgiven for these as he embarks upon a “pure” relationship with his new wife. “You may be a sinner, but I ain’t yet had the opportunity” – well Jack took care of that problem, huh?
The deft use of this prayer as the final scene of the wedding ceremony also allows the Director a smooth yet powerful transition from the conclusion of the wedding to the early (happy) view of Ennis and Alma's married life.
Also significant, if not genius, (I feel) are the very words chosen for Ennis in this scene. When the cut from the kneeling, retching Ennis in the alley to the standing ceremonial Ennis is made he’s uttering the words “lead us not unto temptation, but deliver us from evil”. Who's evil and who's temptation here? I feel Ennis's (Heath's really) wonderful facial expressions here say it all. He's looking confused and worried, not unlike the facial expression we see on the young Ennis when his dad takes him to see the remains of Earl. He doesn't know what to think, the people around him are joyous and happy but he's feeling anything but. His past time of joy and love with Jack up on Brokeback is now reflected in the foreboding of his future life of dreary domesticity with Alma.
Also, to cut back to the SS for a second, I love the way Annie can interject sexuality into the storyline so subtly that you hardly notice. "and had her pregnant by mid-January", Yup ol' Ennis may not have been good with words but he sure was good with sumthin' - no wonder Jack redlined it up to Wyoming. Whoee, Yeah! Nice work Ennis!