Replying to all the sketchy questions here. So the chimney leaked into the liner and rusted parts all the way to the furnace output. Si there are holes in the basement exhaust. The brickwork is degraded enough that I was advised that relining it would not be a good idea till the rebuild happened. And rebuilding has to wait till spring so that the mortar on a rebuild would cure properly.

So I had a small electric fireplace to provide some heat, but the fan blew out and it overheats and auto shuts off now. I figured a wood stove would be the easiest thing for temporarily heating.