Not uncontrolled rage, more like a zen state of transcendent fury, lol. I agree that he'd just been through the emotional wringer, where I disagree is on whether it softened him as a result. I don't think it did. I think any conflict he had about killing/not killing extended to Luke alone and no one else.
To me his quiet exit from the bridge just showed him in a state where he was so beyond being angry at the situation after all he had done to capture and convince Luke that he basically just checked out mentally in that moment. Kind of like Leia's reaction that final time the hyperdrive failed before R2 turned it on. She had been freaking out and lashing out at Han the whole movie and then when it wouldn't work that one last time she was just over it to the point where she too couldn't bother to yell at or scold Lando, she was just done and slumped silently into the chair.
Anyway at the end of the day we're talking about what a guy was feeling who was completely enclosed in a mask and said no words so your interpretation is certainly as good as mine.