Sidebar height

This is not a feature available in the theme as you can see in the online preview. However, you could do a small trick with some custom CSS and enable scrolling in the menu. 

Paste the following CSS code into the proper place from the Theme Options:

#menu {
  height: 70%;
  left: -40px;
  overflow-x: hidden;
  padding-right: 0;
  position: relative;
  width: 290px;

This will make a sidebar appear on the right side of the menu, thus enabling you to use whatever size you want.

It's not the most elegant solution, but still, it works. You could try to add a custom jQuery sidebar with a cool design though, but you need to hire someone for the job.