The analyses of a text #1

The narrator recalls his childhood.
He was forced to work for his own living for Mr. Murdstone's friend Mr. Quinion at London by his stepfather Mr. Murdstone.
When the protagonist started to run away to his grand aunt Miss Betsey, he was robbed his money and box by a porter and then he abandoned pursuing him after a long distance pursuit.
At last, he arrived his grand aunt's place after a long and rough traveling.
He said his own story to his aunt and her friend Mr. Dick, and then he slept in the attic room.
His aunt asks him to give a certain information from Mr. Dick.
Now he thinks Mr. Dick is mad.

"He has been called mad," said my aunt. "I have a selfish pleasure in saying he has been called mad, or I should not have had the benefit of his society and advice for these last ten years and upwards?in fact,, ever since your sister, Betesey Trotwood, disappointed me.'
"So long as that?" I said.
"And nice people they were, who had the audacity to call him mad," pursued my aunt. "Mr. Dick is a sort of distant connexion of mine; it doesn't matter how; I needn't enter into that. If it hadn't been for me, his own brother would have shut him up for life. That's all."
I am afraid it was hypocritical in me, but seeing that my aunt felt strongly on the subject, I tried to look as if I felt strongly too.
"A proud fool!" said my aunt. "Because his brother was a little eccentric?though he is not half so eccentric as a good many people?he didn't like to have him visible about his house, and sent him away to some private asylum-place, though he had been left to his particular care by their deceased father, who thought him almost a natural. And a wise man he must have been to think so! Mad himself, no doubt."
[David Copperfield by Charles Dickens]
1. I'd like to know what "I have a selfish pleasure in saying he has been called mad" here.
2. I'd like to know what "so long as that?" means.
3. And I'd like to know if "so" refers to "mad himself."
Thank you, in advance for your help.