My house has been filled with soot above all my heating vents. I have also had a lot of ghosting, which I think is caused my using lots of candles. My combustion chamber in the boiler is cracked, and I can clearly see the flames shooting on the other side of the crack. Can this be a problem why my hoise is filled with soot above my vents in every room? Is it because the soot may not be flowing through the chimney, but intead through my pipes inside my house?

I would say yes... I also hope you have working Carbon Monoxide detectors on every level of the house too... because I would be concerned about that.

Yes I do, I have a split level home. I have one CM detector on each floor. Thank you for your response.