Alternatively, now that you have gotten your feet wet so to speak and like the combination of i3WM and XFCE why not just use both at the same time?
Read here:
This way you keep all the XFCE goodies and use i3 as the window manager. I have a piggy back post to that one coming but it wont be until later tonight. Since you say logging into XFCE works correctly this should as well since you don’t actually change the session from XFCE to I3 when you log in.