Your right . There is such a thing as loving someone , and then there is being IN LOVE with someone . Ennis obviously loved Alma at some point, enough to plan a life together with her. IMO it was based on what was expected of him to do His brother and sister had married and ennis felt that this is just what a man does. We were not privy to the relationship between Alma and Ennis until the wedding, the rest is up to us as veiwers of the movie to fill in the blanks as to their relationship before the wedding. He may have been pressured to live up to tradition. Anyway he went on to have a family with this woman, after I wonder how many times he thought about backing out. He Did not seem happy at the wedding. All this would feel different to Ennis had he never met Jack, but he did meet him and IMO fell in love with him. More in love than anything he felt for Alma. For four long years I think Ennis just went through the motions of the marriage for several prposes
1. It provided a smokescreen from being "queer" ( could'nt face it) .
2. It provided safety ( no one had reason to come after him and Alma with the tireiron)
3. To convince Jack that it was over after Brokeback ( it was'nt) and Jack knew it .
4 Because he loved her. ( but no real emotion or passion, he pretened she was Jack in bed)!!
With Jack, he had the emotion, the passion,, that love that does'nt fade away with time , the longing evident in the reunion kiss when he practically devoured Jack. Four f#ckin long years of pent up feelings surfaces.It's obvious at this point that Ennis is deeply in love with Jack. Alma was just another excuse for Ennis to use against himself .. He eventually got to that point of accepting his feelings when he said " aint no reins on this one. .......This one? what about the other one? No match, no comparson with the love he had with Jack F, Twist.