The analyses of a text #5

The narrator recalls his childhood.
Mr. Dick, who lives off the narrator's grand aunt, visits the school the narrator goes to every other Wednesday.
Uriah is the clerk for Mr. Wickfield who is the master of the narrator's boarding house, his grand aunt's friend, and a lawyer.

One Thursday morning, when I was about to walk with Mr. Dick from the hotel to the coach-office before going back to school, I met Uriah in the street, who reminded me of the promise I had made to take tea with himself his mother, adding, with write, "But I didn't expect you to keep it, Mater Copperfield, we're so very umble."
I really had not yet been able to make up my mind whether I liked Uriah or detested him, and I was very doubtful about it still, as I stood looking him in the face in the street. But I felt it quite an affront to be supposed proud, and said I only wanted to be asked.
"Oh, if that's all, Master Copperfield," said Uriah, "and it really isn't our umbleness that prevents you, will you come this evening? But if it is our umbleness, I hope you won't mind owning to it, Master Copperfield, for we are all well aware of our condition."
[David Copperfield by Charles Dickens]
1. I'd like to know if "adding" is a dangling participle.
2. I'd like to know what "be supposed (to be) proud" means here.
Thank you in advance for your help.