The bathroom is liveable, the wet rot and concerns about the floor... Run a bloody mile now!
That is a money pit! You will be looking at around 20-30k to have that put right, if it is present in one cpr er then the whole floor in that room will need ripping up, potentially the joists need replacing, the whole house will need treating and allowed to dry out before the floor can be put back down. If it's not done properly you will struggle to get insurance on it.
Assuming you haven't exchanged contracts then walk away now.