You can hold the 'Shift' key, and all the provinces you control will turn a colour to match the happiness of the population: green for 'happy', yellow for 'slightly disgruntled' and red for 'postal workers who were refused a pay raise'. ;-)

Scotland isn't a very rich province if I remember correctly, so lowering taxes won't have a huge impact on your economy, and if you put in some more units than the 100-men minimum the population shouldn't become hostile that easily, but I may be wrong there.