I can open a second pane using alt+cmd+2. how do I switch to the new empty pain and open a file from the keyboard?
Control+2 to focus the second pane.
How to open a file from the keyboard? Up to you... Control-O, Control-P, Control-T, etc...
You should be able to create a .sublime-macro which allows you to string together a number of commands (look in Packages > Default for some examples) and then call it up via the palette or keybinding.
You may also want to look at Origami 1 which provides additional commands relating to panes.
Hope this helps,Alex