Your going to finish it. Have Heart! It is too bad that it is that unstable at times. I don't guarantee that this will work, but it might I just ask it to continue my last save and it did, but without any hotspots so Kate would have to stay the rest of her life on top of the water-tank. No way to get her down so I quit the game again and restarted it and then clicked on Continue, this time I got a hotspot so she could go down. Give that a try. never know. I had my save going bananas the first time I did the Gem puzzle with mirrors. ALT-TABS, etc. and restored it twice to be able to finish it
I also see that you have learned a valuable lesson - Back up your save after finishing a new chore. Gives you something to go back to.