hi, I know how you feel. My dad is an alcoholic, a functional alcoholic (that means he functions fine during the day and can function but drinks alot in the evenings).
There is not really a-lot you can do in terms of getting him to stop drinking, if you are going to try and talk to him it would be best to try and do so when he's sober/not had a drink and is in a good mood.
If you don't feel able to talk to him like in person could you write it down in a letter to him or something like that and let him read it in his own time?
I'm not like sure what country you are in, if you are in the uk theres a place/helpline (they have forums and email too) called NACOA - you might find it helpful to talk to them. their website is
www.nacoa.org.uk
they have alot of information etc on their website, you can also ring them on 0800 358 3456
Even if you aren't in the uk you can still access the website and look at the information on there, if you are in the uk you can ring them on the above number.