Quote 1
"It's not my business," Scrooge returned. "It's enough for a man to understand his own business, and not to interfere with other people's. Mine occupies me constantly. Good afternoon, gentlemen!" (1.65)
Here, Scrooge is more like Dickens's later creations, Mr. Podsnad (from Our Mutual Friend) or Mrs. General (from Little Dorrit)—characters who want to enclose and isolate the unpleasant from their sight because it's just too pesky to deal with.
Quote 2
"Do you know the Poulterer's, in the next street but one, at the corner?" Scrooge inquired.
"I should hope I did," replied the lad.
"An intelligent boy!" said Scrooge. "A remarkable boy! Do you know whether they've sold the prize Turkey that was hanging up there?—Not the little prize Turkey: the big one?"
"What, the one as big as me?" returned the boy.
"What a delightful boy!" said Scrooge. "It's a pleasure to talk to him. Yes, my buck!" (5.19-23)
So, are we thinking that the strange third-person asides here—"a remarkable boy!", "it's a pleasure to talk to him"—are the result of Scrooge having forgotten how to speak to other humans? Like, his isolation has literally rendered him unable to have a normal conversation, so he just keeps exclaiming things to his face?
Quote 3
"Now, I'll tell you what, my friend," said Scrooge, "I am not going to stand this sort of thing any longer. And therefore," he continued, leaping from his stool, and giving Bob such a dig in the waistcoat that he staggered back into the Tank again; "and therefore I am about to raise your salary!"
[…]
"A merry Christmas, Bob!" said Scrooge, with an earnestness that could not be mistaken, as he clapped him on the back. "A merrier Christmas, Bob, my good fellow, than I have given you for many a year! I'll raise your salary, and endeavour to assist your struggling family, and we will discuss your affairs this very afternoon, over a Christmas bowl of smoking bishop, Bob! Make up the fires, and buy another coal-scuttle before you dot another i, Bob Cratchit!" (5.67-69)
So, there we go—Scrooge is completely recovered. How do we know? Because he is now willing to actually touch another human being. Check out how odd it sounds to see Scrooge poking Bob in the ribs and "clapping him on the back." That's how alien he used to be.