How can I keep being angry if he is sick and not realizing he's going off the deep end ?
You can be angry because he's the one that made the choice to begin with to go down that road.
And at the end of the day, it's really not about being angry. If you read enough posts, Jess, you're going to see a pattern. And that pattern is the addict does not have the bandwidth to be a responsible, committed partner because they're too busy self destructing.
As a point of reference, check out posts by a member named mnh1982. Two other members are story74 and YogaGirl; read their posts. And then judge for yourself.
Keep us posted.