I am so sorry that your h has let his son done and didn't respond to your message.
I do think that his drinking comments were a message for you through your son. He was looking for a reaction from you about it and didn't get the reaction he was expecting. Sometimes, it takes days for them to respond back and who knows, you might have caught him off guard when you didn't respond the way he thought you would. He still looks to you as an authority figure.
As for him not liking your son, I don't think that's the issue. I think he resents his son and the relationship that your son has w/you. Many of them will become jealous and resentful of their children because they are still in the "teen" mode and think about how their parents treated them back in the day. Yes, it is your h's issue and he needs to work things out.
As for your son, continue to support him as you have been doing. Some day, he will look back and acknowledge the fact that you were there for him through some of the roughest patches in his life. I do think that deep down, his father does love him, but he doesn't know how to relate to him at the moment.
You have nothing to forgive. You didn't know that your h would flip the switch become the person he is today.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
