I don't want to say definitely yes just yet. But if the CPU can not be properly held down with the pressure it needs than it might be a lost cause. I do have to ask how hard did you have to press? Motherboards are pretty tough but to break one like that is the first time I've heard of it.
Yeah, I think its dead. Like I said without the proper pressure a CPU won't have the correct amount of contact with the motherboard. Even the CPU cooler will not put enough pressure since it's just to contact CPU and really nothing else. If you were to install the CPU and the cooler you would risk the CPU moving around and damaging the pins.
It's worth trying an RMA. If you were having problems with the arm it could be a problems with how it was built. I've never seen one shatter like that. They might accept an RMA to repair or replace it. The worse they can do is deny your RMA it's worth a shot.