Yes agree with your tax assessment, but it does sound low, but as mentioned it maybe a very low price house (83k would be for probably under 2m , as assessed by land Office).
Also to OP...take a a lot of comments with a grain of salt, but you do need to find out if she has definitely been paying the mortgage monthly to the bank, as the Chanoot is physically with the Bank, not with her.
You actually have quite a complicated scenario, so you need to get excellent advice beforehand.