Noramlization Time Series to Predict Stocks exact Price
You should always fit the scaler with the train data. This is one of the typical validation problems, it is hard to replicate train test conditions. 

Have you considered doing rolling/rollout window split?


This way the range of values will be closer between train and test.

THe problem of this is that you loose  some of the training information. On the other hand information about 40 years ago of stock has not much to do when forecastin the present