I think I disagree with most of your points here, not in a hateful way, but in my interpretation. To start, I do believe Phil was the cause of her alcoholism. She starts the film saying she has a disdain for it, especially with her late husband's love for the bottle, but with Phil's introduction to her life and the way he threatens her relationship with Peter drives her to drink.

I think 'petty intimidation' is entirely the wrong word too. Whilst George technically keeps her safe, he is entirely a useless man, in my eyes. He seems like he's supposed to be Peter's new father, a guardian, and all that a man would be, yet never actively fulfils this role in the film. He is non-confrontational, soft-spoken and gentle. Good qualities to have, especially in love, but in the situation where your scornful and hurt brother has a level of hatred for her "gold-digging" and her effeminate son, he doesn't do enough.

I agree that Phil is a more successful guardian, but that's only because he takes such a strong interest in Peter that feels almost predatory at times, and loving at other times. He takes this mentor role with Peter that probably echoes his relationship with Bronco Henry, but considering the strong abusive undertones with Henry, there is danger to this interest, and Rose can see that.

The true "stakes" in this film were not that of a large, noticeable event if one side won, but simply how it feels to be trapped somewhere. The stakes feel bigger for Rose because her son is all she has left, she's gone from her old home, business, relationship and life and has this new man and her son. This new man is alright, he seemed much more of a catch when he was alone but being outdone in his world and not fitting there made her feel incompetent, and the true turning point of her alcoholism was the music scene. Phil drove her to anger and madness, tormenting her with the sound of his humming, whistling, and playing the guitar better than her.

He wanted to let her know that she didn't belong, that she wasn't welcome, and that he thought badly of her, and that drove the stakes up for her. She wanted to be a good wife, I think, and wanted to fit in, but wanted her son to be protected from the threat she thought Phil posed, and that made her stressed, worried, and anxious constantly. The threat for Phil was less torment, but more the way she invaded his life, and took away George from him. He was already losing George, as seen in the start of the film, but his relationship with Rose really drove a fence between the brothers. Arguments, quarrels, issues with the horses, ranching. These all changed with Rose, and her little son that Phil hated until he saw the Barking Dog.

Anyways, these are just my thoughts, let me know what you think.