I get what you're saying but just laying out the facts is usually the best way to communicate difficult things, even to people who are depressed. Unless he's severely clinically depressed, he has times when he feels OK and he can spare some mental real estate to give his son support.
About the pressuring and blaming, he might not have thought about it until you brought it up. I don't mean that to sound harsh but do you see what I mean? It's already in your mind that you think you might be doing that, so you apologize in advance.
What if you had said: H, I want to let you know that S has been having a difficult time with depression for a while now and is seeing a counselor. He gave me permission to tell you. If you want to know more, call S.
What the heck does he do? Has he always worked like that? How did you have a marriage?
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss