You can go to address bar by ⌘ + l / Ctrl + l, but how can I go back to, or focus, the browsing area again?
Pressing esc will "undo" your previous keystroke and eventually take you back to the browsing area. You may have to press esc multiple times though.
[EDIT:] Does simply pressing Tab a few times work for you? [/EDIT]
There doesn't seem to be such a shortcut. What you can do is press CTRL+F, search for a word close to where you are on the page and then Esc.
Of course this is not really convenient, so you could also do what this other answer suggests and type
I hope this helps. Sadly, AutoHotkey is only available for windows but there might be a similar tool for Mac.
Another option I just found out about: On windows, I can press Alt followed by Tab. This might work on mac as well.