MacBook Pro keyboard and Trackpad not working. All solutions found have failed
You need to replace your top case assembly.

Your keyboard and trackpad (built in) are USB devices, so when you plugged in your external mouse/keyboard and everything worked, you effectively ruled out software issues.  This is also confirmed when trying to boot in Safe Mode or doing NVRAM/SMC resets via the built in keyboard.  

If it doesn't work in a pre-boot environment, it's not going to work at all.

The only option left is replacement of the top case assembly itself (Apple PN# 661-02361)  and given that both have failed, it's highly likely that the USB interface on the keyboard has died.

Technically speaking, you could replace just your keyboard and trackpad, but it's an extremely labor intensive proposition.  Whether you are replacing the keyboard/trackpad or the assembly itself, it will require a complete disassembly of the MacBook innards.  iFixit.com has a writeup on the procedure and they rank it as "Difficult" with an allocation of 3 hours time. 

Even if you don't plan on undertaking that repair yourself, I do suggest you familiarize yourself with the procedure to understand what's actually involved.  Suffice to say, it will be an expensive repair.