Answer:
A) The allusion can be found in lines 16 and 17. Mr Whites son had made reference to the fact that if he became an emperor, his father would no longer be <em>henpecked</em>.
B) Mrs White initially took the story about the paw with a pinch of salt. That is she didn't completely believe the story (if at all, that is).
Explanation:
A) To be henpecked means to be bullied or browbeaten.
Given that his son had recurrently beat him at the game of Chess, it was an ironical statement to state that an Emperor, his father would no longer have to endure such.
Recall that in lines 19 and 20 Mrs White had half sarcastically and half encouragingly told her husband that he would win the next game when all three (Father, Mother and Son) knew quite well that he was very bad at the game.
B) In lines 97-99, she had jokingly asked her husband to wish 4 hands for her so that she would be able to multi-task and or have it easier with the domestic chores.
Her disposition, however, changed after the news of the death of their son came with the 200 pounds her husband had requested.
Cheers