YEEESSS I did it !
As 42EspoiR said, when my actor is destroyed, I can’t get the location from it anymore.
So I wanted that, directly when the game start, it simply gets the location from the object.
I start to understand how to “think” blueprint 
Here is the code :
http://image.noelshack.com/fichiers/2015/17/1429814080-pbdelayprob3.jpg
EDIT : But… There is always a little problem… If I want my rectangle actor to respawn fast, there is always a risk that the actor respawn on some debris. And the game seems to crash only if the actor is respawning on some debris coming from a destructible mesh. I hope this will be fixed on an upcoming UE4/UT4 update.
EDIT 2 : Well… I’m wrong, it’s coming from another node group (inside the same blueprint) modifying the Material when the character is overlapping with a box placed just above the “Box_Rectangle” I’ve done. I will report this. So this bug have nothing to do (or not at 100%) with the actor respawning on some debris.