Answer to Question 1
F, G, and K are all similar enough to our Sun to have long life spans on the main sequence, and also hot enough to have fairly wide habitable zones.
Answer to Question 2
Ellipticals were divided into eight categories. He classified the most spherical as E0, and most flattened as E7. The spirals were divided into normal (smoothly unfolding arms) and barred (yellowish bar through the nucleus, then arms breaking off from it at right angles), and divided these into a, b, and c categories based on how tightly wound up the arms appeared, with Sa very tight, and Sc much looser.