Amir is saying when Baba looked at him it made him speechless in some type of way that he couldn’t and was afraid to say anything. Glares are incappable of making a throat dry, making this a use of personifivation.
“A face like a Chinese doll chiseled from hardwood.”
This comparison between Hassan and a chinese doll is to help us view Hassan as Amir did at that time in their lives. They were both just two young innocent kids.
“And from below, the faint sound of water tumbling through the valley.”
Amir is explaining how the water sounded and looked after he had gotten sick in the truck. Maybe he saw the water “tumbling” because that’s how his stomach was feeling after getting car sick.
The darkness is merciful because it hides what Amir sees in the light of the fireworks at his birthday party. The darkness hides the shame and guilt on Amir’s face as he watches Hassan politely serve the people who abused him so horridly.
Baba is exaggerating when he says he wants to invite “the whole world.” He does not literally want to invite every single person, he just means that the more people that attend, the better.
“All I saw was rain through windowpanes that looked like melting silver.”
Amir is comparing two very different things to describe how thick and heavy the rain is. He uses that simile to show his guilt represented by the heavy water.
When the children of the area would say these things to Ali, they were referring to him as a boogie man. The way the children treat him give a mental picture of how badly the Hazaras are treated, as well as how close Ali and Baba had to have been for him to keep him around in a place so discriminative.