One very important thing about kids who grow up poor is that they often lack access to thoughts, ideas, influences, or stimulus from anything outside their immediate environment. And sometimes when they do get it, they don't have the skills to process what they are experiencing. I think this was more of an issue with Ennis than with Jack, but they both suffered because of it individually and together.
More specifically, when it came to their discovery of their feelings for each other, neither of them really knew what to do about it. They were both certainly fearful. And it was something foreign for both. Jack--because he had been exposed to a wider world than Ennis--was at least willing to travel down the path his love laid out for him. Ennis could only react with 1 of 2 primal responses: sex and fear.
Had these two men been less poor, they would have been less isolated. Less isolation in turn leads to broader knowledge, understanding, and experience. So I think their poverty was a major contribution to their tragic circumstances.
What is more, both Ennis and Jack are fairly rough characters, I mean their clothing, behavior, the way they speak, all these things proves the proposition that physically they look like masculine characters, but looking through the inner world perception, both characters (especially Ennis) are very sensitive.
Both Jack and Ennis were indeed masculine to the core. It was not just their clothing, speech, or behavior. And please don't make the mistake of putting masculinity and sensitivity in opposition. The two are not mutually exclusive. I have written much here about the way men express their feelings, both in general and between each other.
If your project needs another topic of analysis in order to fill it out, I suggest an analysis of the relationship between masculinity and homosexuality, and how society has viewed that relationship over time and across cultures. Of course, you'll have to be careful to make sure that your analytical points tie back to the situation in Brokeback. I can point you to a number of resources if you need them.
Buona fortuna col tuo progetto.
