Oooh I love these posts, they've made me think of all kinds of stuff. Unfortunately my brain is a bit fuzzled and I'm not sure that this stuff will come out right, so apologies in advance
The idea of who is the fixer/stander got me thinking about how much of a pragmatist Jack is sometimes, as well as being a dreamer. He stays married because what is the point of hurting Lureen and Bobby, and losing what he's got unless he gets the sweet life. Whereas Ennis wants to stay married for what it shows to everyone outside and what it signifies to himself. Similarly Jack lies to Ennis about being queer because he knows he has to in order to be with Ennis (and I love the way he looks at him as he says it, I always think he's half wondering whether Ennis believes him and half wondering whether Ennis really thinks that he (E) isn't) and about Randell because he is scared of losing him. Jack is aware of his lies and the fact he has to tell them but Ennis's worst lies are to himself.
Also about the way that Ennis 'fixes' stuff on Brokeback made me think that that's another reason for Jack to be so excited about the divorce, I mean up on Brokeback Jack moans about stuff (beans, sleeping in the cat-piss pup tent) and asks for things (elk, no beans, sex with ennis...). At first he gets a refusal from Ennis but then Ennis sorts it for him. When Ennis lets him know about the divorce it's like he's 'fixed' things again for Jack....
The link between how they both fix and stand stuff and with yin and yang is, I think, an important one. No-one is ever all yin or all yang; sometimes people take different positions with different people and within a single relationship there is also this interplay, so despite the way they may see themselves as a fixer or a stander, they actually move between the two poles, often in response to the demand of the other.
Ok, I have no idea if any of the stuff above makes sense, and I'm pretty sure a lot of it is just repeating what y'all have said already. I really should post stuff at times other when I'm about to go to bed!