I've been spending loads of time on this question—if anyone can help me I'll be so happy!
How does Thomas Hardy make Sophy particularly memorable? How does Thomas Hardy portray the power the son has over Sophy?
Hi there! I will suggest some angles you can pursue for questions 1 and 2.
1) How does Thomas Hardy make Sophy particularly memorable?
Here, you could possible talk about how Hardy describes her. He sketches for us a woman who is charming, playful and curious.
Charm combined with mystery:
Although not young, she is unquestionably attractive, her "nut-brown hair...a wonder and a mystery." Even though she uses a wheelchair, and she knows that people stare at her, she refuses to be characterized as a lifeless personality. She is a pretty woman with an "innocent" story, mysterious, but approachable.
..she expected their glances, and did not mind gratifying their curiosity, she met the eyes of several of her observers by lifting her own, showing these to be soft, brown, and affectionate orbs, a little plaintive in their regard.
Playfully mischievous and good-natured:
His mother hastily adopted the correction, and did not resent his making it, or retaliate, as she might well have done, by bidding him to wipe that crumby mouth of his, whose condition had been caused by surreptitious attempts to eat a piece of cake without taking it out of the pocket wherein it lay concealed.
Curious and open to life's details which encourage and comfort her:
Wrapped in a cloak, it was soothing to watch and sympathize with them when depression and nervousness hindered sleep, and to see how the fresh green-stuff brightened to life as it came opposite the lamp, and how the sweating animals steamed and shone with their miles of travel.
Young at heart, child-like, and able to enter into any brief joy opportunities afford her:
When Sam invites her to ride up to Covent Garden with him, she refuses at first, but then with glee and "trembling with excitement, [she] hastily finished her dressing, and wrapped herself up in cloak and veil," ready to go with him.
2) How does Thomas Hardy portray the power the son has over Sophy?
a) Sophy's son corrects her grammar. His education has not made him more compassionate, nor more loving towards his mother. Instead, he is ashamed of her and does not bother to hide his disdain. Randolph's character represents the snobbishness and pedantry of the educated classes in Hardy's time. He corrects his mother's grammar because he feels he is superior to her by way of learning and position; he, after all, is a Church of England vicar's son and his mother a mere servant who married into the Establishment.
b) He will not assent to Sophy's marriage to Sam and makes his mother kneel before a cross and promise him that she will never marry Sam. He holds ransom her motherly affections and uses it as a malicious emotional weapon to subjugate her will to his. He further taunts her with a self-righteous "I owe this to my father!"
Hope this helps with some ideas on how to approach these questions.