Cool topic. I think what you wrote in the initial post is a convincing interpretation Penthesilea. So my question is ... if Ennis = mules and relationship = bear, then what is Jack's animal? I think elk is also a symbol for their relationship... I think elk specifically functions as an aphrodisiac (I've posted about this in other thread), but I think elk could be expanded to be a symbol of their love. I think the bear as a symbol of the entirety of their relationship (all the different aspects of making the relationship happen... not just the love) is very good.
The idea with the bear as symbol for their relationship is not mine, I read it somwhere (back on TOB, I believe).
As for Jack's animal: I just had this idea about Ennis and the mules, I saw the similarities triggered by what I mentioned in my OP, but didn't think of Jack in this case.
But thinking about it after your question, I agree with what Front-Ranger said: it has to be something with wings. Must not necessarily be an eagle, like she said. But birds in general or even an angel could do it for me.
This fits with the wind as symbol for Jack. Wind/air/sky/birds - on a symbolic level, it's all the same: a being not bound to the ground of the earth (like Ennis is). More free and less bound.
Like Jack is more free to set himself above the rules on the earth: shoot a sheep, f*ck Aguirre, leave his wife, love another man and live with him, leaving his home farm and living footloose on the rodeo circuit, and so on.
After his death this thought can be continued: angel/heaven. In my language, the word for sky and heaven is the same, we have only one word for both. So for me heaven=sky=up above.
And what do humans become after their death? They go up to heaven and become angels.