I'm having a hard time maintaining the faith that kid will grow to recognize his issues when I have zero experience with divorce or alienating parental behavior.

Stop. Stop not believing in yourself. You are protecting your kid. Your ex is not.

Put yourself in your kid's shoes. You love both parents. One is spitting hate, insult, and cruelty. The other is calm, measured, rational, and reliable. Which do you trust?

With another adult, you'd have a smack down. You'd tell the whole truth and nothing but the truth. You'd put it all on the line and let them judge. But this kid can't handle that, doesn't deserve it, and can't emotionally process it. So you withdraw. You tell enough of the truth, when you can. You speak in positive tones, you don't make accusations, you do your best, and you love him through the confusion.

What is going to happen is that someday, someday soon (probably too soon) he's going to realize he's being punked. And he's going to be pissed. And what's going to fucking suck is you're STILL going to have to be the bigger person, the calmer person, the rational one. Because, ultimately, it is up to him and his dad to work this shit out. You can't help him do that. You can't take sides or tell stories out of school. You have to be the grown-up, because no one else is going to be.

Then it gets worse. The ex is going to accuse you of poisoning the kid against him. This is all you, all your doing, how could you! And you're, once again, going to have to be the adult and not kick him the shins. Not piss in his rose bushes. No, you're going to listen, not react, and walk the fuck away. Because you have to be the grown-up. Because no one else will be.

But then, glory! Your kid becomes an adult. Or close to an adult. Adult enough to make his own choices as to where he spends his time and energy. And he'll see dad and his toxic wife and their vitriol and poison and he'll have NO TIME for that bullshit. But best of all, he'll see you. The mom who loved him, who never bad-mouthed, who didn't make it a contest for his love, and who was always there for him and him exclusively. He'll come to consciousness about adult relationships and the awful things people do when they are mad and unable to handle life. And he'll hug you, thank you, and be grateful you were his rock.

Then all you'll have to listen to is your ex pissing and moaning about why your son won't bring the grand kids to Christmas as a grown-ass adult and you'll know you won. Its the long-game, but it pays off because he's going to be the one bemoaning why his own son won't speak to him at 60, while you're playing tea party with your grand-daughter someday.