Young people will naturally get enough practice. When playing octave, the wrist is relaxed and slightly pressed down. It can be said that the octave is more driven by the wrist, so we should pay attention to the practice of the little finger.

It doesn't matter if it is below 8 degrees. You can play as Boeing. In fact, it doesn't matter whether it can reach 8 degrees. Some chords have ten degrees, so you can play them even if your fingers can't reach them, and you can play everything well with solid basic skills.

If you can't grow your fingers, you should practice more, master the position and accuracy of skilled keys, and practice Hanon more.

PS don't break your fingers, which will not only have no effect, but also enlarge your joints.