No doubt that man was well over the limit.
Lowering the limit would probably have little effect on people like that.
However, even a very small amount of alcohol can impair a person's ability to drive as well as they should.
Can you define "a very small amount"? I wouldn't be surprised if most people have very small amounts of alcohol in their bodies for some definition of "very small".
What is the increased risk of somebody driving at just below the legal limit compared to somebody driving sober or with whatever reduced limit you are proposing?
I have never had any alcohol before driving. I have never been drunk. My husband's medication makes it unwise for him to have a drink, so I don't either. I don't miss having a drink, neither does he.
That's very admirable. However, what do you think the risk would be if somebody went out for dinner, had a glass of wine with their food and then drove home an hour later. How impaired do you think they would be? What do you think the increased risk is? Should they lose their licence?