Answer:
(1)Although he's not very proud of his wealth, the old man is rich.
(2)The thief escaped when it was dark.
(3)I saw the boy, he won the medal.
(4)Raj is very silly, she will believe anything.
Explanation:
The first one is his, the second one is whom.
B. I assume because none of the other words would make sense in the sentence when it has the word of. XD
It looks perfectly fine the answer is well said and has supporting sentences to prove your statement. Wording is a little of where you said "but shows even more in the second half." It's not that big of a deal but just kind of rolls of the tongue weirdly not a necessary change but just thought I'd point it out.