I don't believe a bug is causing this as It's working here. Like all things linux, it will be a one liner somewhere that will fix it.
Would you please post your /etc/bumblebee/bumblebee.conf and xorg.nvidia.conf in the same directory.
The way it works is that nvidia-uvm depends on the nvidia-current module. We know that works because you can use optirun glxspheres.
Did you have any useful dmesg feedback from after the modprobe?
Did you add the cuda libraries and then run ldconfig? I'm sure you did, but I was just going through the feedback you posted (I assume you omitted doing it because I didn't ask for it)
Hopefully we can get this sorted out soon
