For me, I feel like some boundaries can be just known to you and you act on them. Others will need to be stated.
Granted, in the beginning I have been "loud and proud" of my boundaries. Calling out the abusive names I've been called and that I will no longer tolerate it. I wonder if my speaking out loud about abusive behavior I no longer want in my life was both for the person hearing it...but more so, to hear myself say it. That the person that needs to understand the boundaries the best...is me.
I've got similar stuff with a brother that says he wants to find common ground/compromise yet balks at any invite to actually talk about stuff. It's really weird honestly. I'm not going to hold his hand.
like you said, e-mails don't get returned, phone calls don't get returned, etc. Sometimes he responds sometimes not. I'm trying very hard not to take control (ask for a third time and I'm now trying to control). I try to know what I want and act on it. I WANT to have that difficult conversation with him, but he also has to be willing. What's odd, is the one I'm talking about we're not officially estranged and I don't think he has a drinking problem to my knowledge.