It seems there are many references including the numbers in the 40's .I wonder if it is a deliberate link to the fact that Jack never made his 40th birthday, as in " he was only 39 years old" when he died, as said by Lureen on the phone to Ennis.
That however may be a leap too far but I always felt it was very poignant.In that he never reached the big 40 as it is often referred to.
Probably the 2 most cataclysmic events in Jack's life, one good, one horrendous, occurred in the last year of a decade.He met and fell in love with Ennis when he was 19 and he dies when he is 39. Yet separating those 2 odd numbers is 20 the number of years he knew Ennis. A very even number and in sharp contrast to the 19 and 39.
The 19,as in the age of Alma junior when she tells Ennis she is getting married, surely has to be reference to both Jack and Ennis.They were both 19 when they met, and Ennis had the opportunity to grab what hopefully Alma is going to. A happy life with the one they love.He blew it so we hope in direct contrast Alma will grab it with both hands and run.
It is very poignant that Ennis asks if Kurt loves her, not the other way round.
Jack loved Ennis and he now knows it, in the same way he can finally accept that he loved Jack. The contrast is stark.The melancholy of Ennis all the more apparant.