Let's back up.
He was drinking for years? that you didn't know he was. So he had a mistress as an analogy, and you didn't find out about her, but you were ok with your relationship until you found out.
A couple reflexes are triggered. The first is the feeling of being cheated on. Sneaky business. First reflex...I will CONTROL his behavior with ULTIMATUMS. He immediately violates your demands, and sees the mistress again. You find out.
First lesson--YOU CAN'T CONTROL HIM.
So here comes the big question. If we don't put a P.I. on the guy 24/7, how are we going to know if and when he is doing sneaky business? In your reality--a breathalizer.
To do so would be trying to control him. We have to let go of that.
So what do we do then?
As is often said here, a boundary is for ourselves. We don't even need to share it with the addict, in fact, it is to our benefit if we don't, so that they can't manipulate with that knowledge.
I might try focusing on the behaviors that he exhibits that bother you. You can't nail when he's been drinking, as you know from the past. If you couldn't tell, and you were ok with him, then what is the complaint? You have to find the behaviors that make your relationship dysfunctional, and try to focus on those.
I think the valid complaint here is a lack of honesty. He gets a pass for drinking, because you don't know when he has been, so there hasn't been problems from when he has been drinking, unless you expand upon that...I'm going with what you wrote...obviously there could be things you didn't highlight...and obviously your relationship with him would have been different all this time if he hadn't been drinking throughout it...in ways we can't imagine.
We can't control another person. We can though decide that we have boundaries with honesty and openness in our intimate relationships. That's a matter of respect. If someone is lying to us, they are disrespecting us.
I would go with that angle when speaking to him about it.
Problem is...once again...we can't force a person to be honest...and we can't nail them when they're not sometimes...it sounds like he's really good at gaslighting you...it's up to you to have a boundary about his behaviors that affect you. If you didn't know...how do you know HOW it affected you?
It's a sneaky person's dream to get away with stuff, the person not able to call them out on it, and can't even state how they are affected by it.
I would ask myself "How has his drinking affected me?" to get to the root of what bothers you...currently he's in a great position to say to you--You just want to control me, my drinking didn't affect you since you didn't voice complaints while you THOUGHT I was sober....
I'm brainstorming here on this one...some guesswork definitely involved in my response, clarify as needed....