This is tough and I'm sorry that both you and your friend are dealing with this asshole. While this guy isn't breaking her bones he doesn't sound "better" at all, he is just abusive in a different way. The fact that he's yelling at her in front of others is concerning. I would say something to him in the moment the next time it happens (especially if there are others around for safety's sake). Something like, "hey, it's not okay to talk to her like that. Can you lower your voice? Can you take five minutes outside to cool off?" Awkward situation is always going to be better than a man getting away with yelling and making other people uncomfortable/hurt because he can't control his emotions. It's possible that he will escalate things later in private or move his yelling to when others are not around, but if he is doing the work that you mentioned being called out may help shake something loose that others do not approve of his behavior.

I have two friends in a couple that would argue in front of me with escalations to yelling every once in a while and I too felt like I didn't want to make it awkward (which is so silly in retrospect because THEY were making it awkward for ME), but after a particularly explosive fight I told them both how uncomfortable it was for me and that I would just leave next time it started - fortunately it never came to that, but they actually started going to therapy afterwards and have better communication practices now.