Glad the book recommendation from Jabiru was helpful, and that it gave you more action ideas vs just theory

I do make boundaries around the rages but they don't stop the rages from happening.
As odd as this sounds...
well, yes,
exactly.
Our boundaries are for our own protection. They do nothing (directly) to impact the behavior, thoughts, feelings, or actions of others.
It's kind of like having an umbrella. You can have an umbrella and open it when it rains. Opening the umbrella has zero impact on the rain... but it does protect you.
If a boundary you have (a rule for yourself) is that you don't stay in the same room with someone who is raging, and then, when you're in the room with someone who is raging, you exit and go do something pleasant, and the person keeps raging alone...
then your boundary
is working -- because it's all about you making choices about what you allow into your life, and you having rules for yourself about what you're up for and how to protect yourself.
Which makes me wonder if my simply staying with him makes him feel validated and think that raging is okay in the end, bc, after all, I am not leaving him. In other words, I wonder if the "consequence" is not strong enough to inspire a change.
It's hard to say. We don't have any (direct) control over what someone else thinks, feels, or perceives. I'm not sure there's any perfect move we can do, that can guarantee that another person will "think correctly" about the situation.
How does he respond (if at all) when you exit the room when he's raging?
I know this is my piece to work out--the boundaries piece. Perhaps I need even stronger boundaries.
What would that look like to you? Again, remembering that if he continues his behavior, that's not necessarily because you have weak boundaries.
...
I will add that it's human nature that we respond to changes that others make. So it's not like there's no possibility that he'll "change his tune" after you follow your own new rules for yourself for a while. That's just what people often do. It's like if for a while my carpool driver was on time, but then for a few months was 5-10 minutes late, then even though technically the driver isn't "making" me do anything, my behavior will probably change (I want to be on time so I'll drive myself).
The concept of
extinction bursts could be helpful as you learn more about boundaries and committing to following your own boundaries for yourself. Extinction bursts are a way that some people respond to boundary changes in others. It can help to know more about it ahead of time.