The analyses of a text #2

The narrator recalls his adolescence.
He was an apprentice for Mr. Spenlow.
He and Mr. Spenlow's only daughter Dora fell in love with each other, but after Mr. Spenlow's sudden death, she moved in with her two aunts.
Now he is going to be married to Dora.
Miss Lavinia is Dora's aunt.

....................................................
Another happy evening, quite as unreal as all the rest of it, and I steal into the usual room before going away. Dora is not there. I suppose they have not done trying on yet. Miss Lavinia peeps in, and tells me mysteriously that she will not be long. She is rather long, notwithstanding; but by and by I hear a rustling at the door, and someone taps.
I say, 'Come in!' but someone taps again.
I go to the door, wondering who it is; there, I meet a pair of bright eyes, and a blushing face; they are Dora's eyes and face, and Miss Lavinia has dressed her in tomorrow's dress, bonnet and all, for me to see. I take my little wife to my heart; and Miss Lavinia gives a little scream because I tumble the bonnet, and Dora laughs and cries at once, because I am so pleased; and I believe it less than ever.
'Do you think it pretty, Doady?' says Dora.
Pretty! I should rather think I did.
[David Copperfield by Charles Dickens]
1. I'd like to know what "the usual room" means.
2. I'd like to know if "is" means "takes."
3. I think "I believe it less than ever" the abbreviation of "I believe my pleasure is less than ever."
So I was wondering why it is "less," not "more."
Thank you in advance for your help.