Scrooge has many layers blocking others from seeing the real him (money, individualism). Spirits attempted to break the wall, but no one else did because his "sharpness" pushes them away, like how he hurts Fred.
Symbol of your actions, good and bad. Your chain can drag you down and weigh you down. It can be like a disease that torments you because of your doings in the past life.
Rather than regret and burdens being heavy on his shoulders, they have started to very slowly loosen and connect with joys and hopes - first sign of change.
Ghost of Christmas Present: '"MrsCratchit made the gravy hissinghot; Master Peter mashed the potatoes with incredible vigour; Miss Belinda sweetened up the apple-sauce"'
Ghost of Christmas Present: '"The house fronts looked black enough, and the windows blacker, contrasting with the smooth white sheet of snow upon the roofs, and with the dirtier snow upon the ground"'
"Smooth white sheet of snow" above is the rich just relaxing, and the reason for their relaxation is because of the hard working poor at the bottom represented as "the dirtier snow upon the ground".
The boy is a symbol of society's ignorance (especially the wealthy) of the lower class' suffering, turning a blank eye to it. The girl shows people who want the basic needs, water, food, shelter. This is purposefully done through children to make the feel empathy, pulling on Scrooge's heart chords, but also us.
Scrooge realises he must change or his end will be of destruction in dark and gloom. "Overrun" no one is taking care of him like un-kept weeds. His time is coming to an end- where he snaps.
Repetition of "I am" shows the constant affirmations since he has never experienced this feeling of self-freedom and true happiness. Simile "feather" shows how this burden has been taken off his shoulders and that he will not carry the chains like Marley did. And "angel" contrasts with how Scrooge was a sinner.