I guess the maths says, that if he has cut down drinking to "only" 5% of the time now, he should be able to cut that out to zero very soon.
Assuming he is awake 18 hours a day, it means he is not drinking for 17 hours 6 minutes a day, unless he is also adding his sleep time as part of his non-drinking time, which would mean a non-drinking time of 22 hours 48 minutes.
He only needs to not drink for period of 1 hour 12 mins (24 hr period) or 54 minutes, to be stone cold sober the whole day.
Frankly, I have never known anyone who drank til they became a drunken fool, and only being a drunken fool for at most 1 hour 12 minutes.......the ones I have known drank til they became drunken fools, and stayed that way for more like 15 hours a day.
I think I would be detaching from him ASAP Serene, because he is obviously in some different land to where you live, and you do not want to go there.
God bless