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 call for Mr. Dick but says Dick is an alias and his true name is Mr. Richard Babley.


.................................

"But don't your call him by it, whatever you do. He can't bear his name. That's a peculiarity of his. Though I don't know that it's much of a a peculiarity, either, for he has been ill-used enough, by some that bear it, to have a mortal antipathy for it. Heaven knows. Mr. Dick is his name here, and everywhere else, now?if he ever went anywhere else, which he don't. So take care, child, you don't call him anything but Mr. Dick."

[David Copperfield by Charles Dickens]
1. I'd like to know why it is "that," not "if."

2. I don't know what "either" means here and I think "either" should be "or," and that "for" should be "because."

And I was wondering why "it" is "either, for," not "or (it's) because."
Thank you in advance for your help.