The analyses of a text #1

The narrator recalls his adolescence.
He came to the local lawyer, Mr. Wickfield' house, which he boarded at as he went to a school, after a long time.
Mr. Wickfield's only daughter Agnes is his best friend and counselor.
Mr. Wickfield's partner Uriah Heep and his mother live with Mr. Wickfiled in Mr. Wickfiled's.
Uriah Heep had confided to the narrator that he was crazy for Agnes in London.

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'Do you suppose,' said I, constraining myself to be very temperate and quiet with him, on account of Agnes, 'that I regard Miss Wickfield otherwise than as a very dear sister?'
'Well, Master Copperfield,' he replied, 'you perceive I am not bound to answer that question. You may not, you know. But then, you see, you may!'
Anything to equal the low cunning of his visage, and of his shadowless eyes without the ghost of an eyelash, I never saw.
'Come then!' said I. 'For the sake of Miss Wickfield -'
'My Agnes!' he exclaimed, with a sickly, angular contortion of himself. 'Would you be so good as call her Agnes, Master Copperfield!'
'For the sake of Agnes Wickfield - Heaven bless her!'
'Thank you for that blessing, Master Copperfield!'he interposed.
'I will tell you what I should, under any other circumstances, as soon have thought of telling to - Jack Ketch.'
[David Copperfield by Charles Dickens]
1. I'd like to know what "come then" means.
2. I'd like to know if "good" means "great" here.
3. And I'd like to know if "should as soon" means "would rather than."
Thank you in advance for your help.