Phew! Those old chimneys are a lot of work to fix.

My house, an old farm house built in the early 1800s, it had similar leaky old chimney problems years ago when my cousin was living in it. She ended up just building a whole new chimney on the outside of the house, offset from the house by about 60cm, but held onto the house by long steel brackets. Being completely outside and away from the house like that, it does not heat the house as efficiently as an inside chimney would, and it fills with creosote and requires cleaning more often. But at least if there is a flue fire there is not as much danger of it spreading to the rest of the house, I guess.

I still hope to fix my old inside-chimney someday, but I think I will have to completely tear it down and build a whole new one. And there are so many other more pressing things that need to be fixed! I think I may just buy one of those outdoor wood furnaces that circulates hot water into an indoor heat exchanger instead, and just keep the wood stove in the kitchen for when the power is out.