How do change focus from the address bar back to the document after CMD+L?
You can ⇥ back, or alternatively ⇧⇥ which is usually faster.

It takes me two presses of ⇧⇥ to get back from the address bar to the page: one to move to the Add to Reading List button and one to get back to the page. This may be higher if you have the back/forward buttons on the toolbar, and lower if you have Full Keyboard Access disabled in System Preferences.

You can use Keyboard Maestro to create a macro which lets you get back to the page with a single keyboard shortcut.