The analyses of a text #3

The narrator recalls his childhood.
He goes to the new school Doctor Strong's after experiencing the hard work at a warehouse at London during half a year.
Doctor Strong's wife's mother Mrs. Markleham, whose alias is the Solder, talks to John Jack Maldon whose cousin is Doctor Strong's wife at Doctor Strong's birthday party.

"Yes, John," returned the Soldier. "Virtually an old married woman. Although not old by years?for when did you ever hear me say, or who has ever heard me say, that a girl of twenty was old by years!?your cousin is the wife of the Doctor, and, as such, what I have described her. It is well for you, John, that your cousin is the wife of the Doctor. You have found in him an influential and kind friend, who will be kinder yet, I venture to predict, if you deserve it. I have no false pride. I never hesitate to admit, frankly, that there are some members of our family who want a friend. You were on yourself, before your cousin's influence raised up one for you."
The Doctor, in the goodness of of his heart, waved his hand as if to make light of it, and save Mr. Jack Maldon from any further reminder. But Mrs. Markleham changed her chair for one next the Doctor's, and, putting her fan on his coat-sleeve, said:
[David Copperfield by Charles Dickens]
1. I'd like to know what "as such" means here.
2. I'd like to know if "one" implies Doctor Strong.
3. And I'd like to know if "Mrs. Markleham changed her chair for one next the Doctor's" implies "there is a vacant chair between her and him."
Thank you in advance for your help.