"Across from" specifies that you're facing each other, "in front of" doesn't. You could be facing in the opposite direction of someone if you're standing "in front of" them, like if you're in a line together.
Brand new word, "overfor". So why is it not included in the table in "Tips and Notes"? I often find the unit "Tips and Notes" to be lacking. I don't know where else to bring this to the attention of course designers, so I put it here.