I'd add more backstory to Tiny Tim so we can have more reason to feel sorry for him other than just a kid dying.
Oscar Wilde once said about one of Dickens' characters:One must have a heart of stone to read the death of little Nell without laughing.
But anyway...I wanted to speak to this:
Normally when it comes to storymaking, I've often favored the principle that the audience's initial impression of the protagonist must be a favorable or sympathetic one. Scrooge runs in opposition to this notion as a grumpy character absent of sympathy. He was a rather interesting character and fun to watch for Carreyisms however. I guess disagreeable protagonists can be entertaining, like the Grinch. I've never read the book, but if I were to rewrite this, I'd immediately start the story right at Scrooge's past and show some warmth. And then more how and why he became so grumpy.
Having a character that the audience can distance themselves from can also be a successful technique. As I Lay Dying
has almost zero likable characters, but is a blast to read, likewise basically anything written by Flannery O'Connor.
I think it would be a mistake to try to get sympathy for Scrooge right off the bat. You're supposed to hate him and want bad things to happen to him, and then bad things do
happen to him, which is kind of a reward for the audience. But it also makes the audience uncomfortable because when we see Scrooge's unhappy past and his change into a charitable character, we feel a tiny bit guilty for passing judgment earlier.