Some things I learned today:
1 - Never used toolkits. You won't know where they failed.
2 - Fight till the end
3 - Be CAREFULL with stuff you're using in your rooted N7, even if it's a highly recommended app from play store like LCD Density (Yep, that one screwed me up real good).
I almost died today when my fully functional and rooted N7 gave me only a black screen after rebooting to apply changes from LCD Density. I tried flashing stock rom twice using the same toolkit that helped me root it, but no deal. I was stuck at the "X" logo on boot forever. Guess what, like it was said on the first page, simplest solutions are often the solutions. The deal is that the commands to erase cache, recovery and system using fastboot will not succesfully complete if your device is plugged in your PC using a USB port from the front panel. I was only able to find this out when I was following this guide, as the feedback to the user from fastboot is given to the user without any kind of filter from a third-party tool. I switched to a rear USB port and all commands finished smoothly, and a tear went through my cheek when I heard the N7 first boot sound. Thank you Hollip3020 for the feedback regarding the USB port, and I wonder if our friend fenderjelly tried this... Maybe it's not too late for him, I will try sending him a message about this right now.
Thank you all, and Remember: Use a rear USB port to connect your device to the PC. It worked for me.