1. Not exactly. "Difficult to place" means that it is difficult to make connections to other similar things. For example, a painting is often understood in connection to other, similar paintings from the same time period. "it is difficult to place Pablo Picasso’s other massive painting on the subject of conflict, War" means that there are not obvious visual connections to other works from the same period, so it may be difficult to "read" or "understand" this painting. In this case, it is difficult to know if the painting is a response to the Korean War or not.
You can use "hard to place" or "difficult to place", they have the same meaning.
"Hard to place" also has another, different meaning; seeing someone for the second time, it is difficult to remember the first place you saw them.
"I definitely know that guy, but it's hard to place him" (I recognize that guy, but I can't remember where I met him before).
2. Yes, exactly.