Century home, jacking up 1st floor ceiling, any advice?

Hey just looking for some feedback. I own a home that is about 90 years old. Stone foundation unfinished basement, two stories and an attic. The house is about 20'x15' across, and the second floor floor sinks in the centre about 3 inches from wall to centre (where the sinking is the worst). The first floor is ok, with some posts in the basement, and it appears that there probably WAS originally a central post on the main floor, which was removed to open the space up. I'm pretty confident that is what has happened and the floors upstairs are uncomfortably slanted (like I said, basically slants over 3 inches over a 10' run, then lifts back up again for the next 10' to the other side of the house). The basement is level and the main floor is level and well supported with posts in the basement. I hope I've explained that clearly.I was looking up how to potentially level the floors, and was looking at the poured leveler or laying plywood down (the floors upstairs are currently tongue floorboards. But there are two rooms that both suffer from the slant, plus who is to say that the slant won't get worse over time. Plus, it seems to me that jacking up the main floor ceiling could solve the entire upstairs rather easily. I am happy to put a post in the main floor if it means straightening out the upstairs. Even if I could get an inch and a half of lift out of the potential 3", I'd be happy.Does this sound like a good plan? Find a central joist, buy a jack stand, and incrementally bottle jack it up every so often? Then just case it in and be done with it? I realize that this may cause some cracks in my drywall and ceiling as things shift, but like I said the floors are unbearable so I'll exchange finish work for straight floors. Has anyone done this before? Any advice/words of caution/encouraging tales of success? Thanks!