Are you sure you're not hitting power down?
Holding volume up while powering on the device brings you to bootloader mode, from here you can get to recovery. Even if you had no recovery it would get you to bootloader mode. And if you had no bootloader the tablet would show zero signs of life whatsoever
So either you're not pressing keys correct or keys are broken
Also I would advice to stay away from toolkits, often these are far more trouble than they are worth, especially for nexus devices.
If you are able to boot to your stock os, which it sounds like you can, turn on USB debugging and open a terminal on PC
adb reboot bootloader
Get you to the same spot as the key press does
Sent from my Nexus 4 using XDA Premium 4 mobile app