Marley is saying on the quote on page 17 that he used the world’s people to feed his profitable business. He used people’s feelings, peoples generosity to get his own money. That is at least what I think. The way Marley did business got him landed where he is, as a specter, an apparition. He was warning Scrooge that if he did not change the way he did business, he too would end up as a ghost like Marley.
What does forbearance mean? Whatever it means, it will probably have to do with the way that people act pertaining to Marley’s business.
This quote could also be interpreted that he used people in a positive way. I do not think that is the case, though.

