I think one of the reasons he talks different to his vendors is because they talk different to him. I think it's taken the both of you to get to this point with your behaviors & communication towards each other. There is an unhealthy codependency between you. In a way, you've trained your dragon to be this way.
If you begin to change your responses to him when he speaks to you in a negative way, then if it's in him - he will change also, in time. If you don't initiate communication in a negative or controlling way, then you most likely won't be fed negativity back.
You just said it in your post: you would have normally got mad, called him out, told him off.
I think it's been great for both of you to have this break. Maybe he will realize what he accomplished on his own this time: he detoxed, saw his doctor, and followed through with his goal to get this shot. I think he needs to see that too. It sounds like a great accomplishment for him! He can "hike up his britches" on his own, but maybe he struggles with believing this due to the codependency that still exists between you.
Here is a question for you: how do you feel knowing he accomplished all this without you there? Are you focusing on his angry tone because it sort of makes you feel like you’re in control? Like yes he did this, but he wanted me there and didn't get what he wanted, he is unhappy. Score one for me?
I hope my comments don't offend, because they are truly meant to provide my insight and maybe make you see a different perspective. Put focus on your codependency issues. I'm happy to hear that you are having a nice trip. I hope you enjoy visiting with your sister over the weekend.