Considering the original questions ....
'Is it better to have loved and lost?'.
The old saying, 'It's better to have loved and lost, than to never have loved at all', I think is true.
'Were Jack and Ennis cursed or blessed?'
If the saying above is true, they were blessed.
They were apart more than they were together, yet the love didn't die.
So, it wasn't just sex, or lust. They were friends who were also sexually attracted.
We can't be someone's friend without loving them, and we can't love someone without being their friend.
And if there is friendship AND sexual attraction (as distinct from sexual appreciation), that is being IN love.
Whether we are together or not.
I'd still rather wake up next to my best friend than a partner that I may love but not like very much.
And that is well said, Scott.