Did the express just say to feed her son poison ? !!

I believe it's not poison, she specifically asks if it will not kill him, I think is a drug to make him more guiable for the things she wants him to do, to not question and disagree with her

More gullible than he is now ? Well, she is twisted so …

Well, he did said to her that his brother should stay in the country (?) because he's too afraid of going to war, when what she wants is for him to stay far away from them, so he's kinda of rebelling