How does Scrooge feel about the fact that people avoid him on the street? How does he feel about Christmas and marriage? Why?

We are told that nobody ever stopped Scrooge in the street to inquire after his health, no beggars ever asked him for money, no children approached him for the time, and none ever solicited directions from him.  

But what did Scrooge care?  It was the very thing he liked.  [He preferred to] edge his way along the crowded paths of life, warning all human sympathy to keep its distance [...].

In other words, this is just the way Scrooge wants it to be.  He doesn't want to interact with others any more than necessary.  He doesn't want friends; instead, he desires solitude.

To his nephew, Scrooge complains that Christmas is 

"a time for paying bills without money; a time for finding yourself a year older, and not an hour richer; a time for balancing your books and having every item in 'em through a round dozen of months presented dead against you?"

Scrooge is most characterized by his greed and lack of charity for others.  He has no compassion and no empathy for the plight of the poor (or anyone else, for that matter).  So, to him, Christmas seems wasteful.  It is a time when those who cannot afford it spend money frivolously, a time when we look back on the year and most of us find that we haven't profited at all (and, for Scrooge, financial profit is really the only kind that matters).  

Likewise, Scrooge scoffs at the institution of marriage or the possibility of love.  He asks his nephew (whose name we don't learn until later on, but it's Fred) why he got married.  Fred replies that he fell in love.  

"Because you fell in love!" growled Scrooge, as if that were the only thing in the world more ridiculous than a merry Christmas.  "Good afternoon!"

So, as low as Scrooge's opinion is of Christmas, he ranks love even lower.  Scrooge finds his nephew -- and the importance his nephew places on everything Scrooge judges to be ridiculous -- so repellent that he dismisses him immediately.  It is as though Scrooge simply cannot stand to hear any more.

Scrooge is most characterized by his greed.  He is

Hard and sharp as flint, from which no steel had ever struck out generous fire; secret, and self-contained, and solitary as an oyster.

He prefers to be alone and finds any and all company irksome at best.  However, it is his lack of compassion for his fellows that is especially damning.  When two men approach him requesting a donation to help the poor at this cold and difficult time of year, they tell him that many of the poor would rather die than go to the workhouse.  His response?

"If they would rather die [...], they had better do it, and decrease the surplus population."

In short, Scrooge cares for his money and little else.  Perhaps one reason for this is that he has learned that it can be difficult to rely on other people, but money will never abandon him.  In Stave 2, the Ghost of Christmas past shows Scrooge his childhood, and in the first scene it seems as though the school is empty of children.  However,

"The school is not quite deserted," said the Ghost.  "A solitary child, neglected by his friends, is left there still."

This child is Scrooge.  He spent a great deal of time alone, sent away to school by his parents, "with too much getting up by candle-light, and not too much to eat."  He knows how it feels to be poor and hungry, and this knowledge likely fuels his need to accumulate.  

As Scrooge grows older, he falls in love with a woman named Belle, but he postpones their marriage so that he can earn more money.  She confronts him, saying that he has grown to love money more than he loves her and that she has "seen [his] nobler aspirations fall off one by one, until the master-passion, Gain, engrosses [him]."  Belle's leaving seems to be the last straw.  Finding himself once more abandoned and alone, Scrooge's character hardens to the point where he is nearly beyond all redemption.  

Having been sent away by his parents, neglected by his friends, and abandoned by the woman he loves, Scrooge has learned that people leave and money doesn't.  People let us down, but money is reliable.  It certainly isn't justification for his callous treatment of others, especially the poor, but Scrooge's history does help to explain how he ended up the way he did.