I take it you knew you could brick it going in and would accept the loss. Here these run well under 90 bucks so bill paid and lesson learned.
As to twrp.img and such, if there is any support it would be on the forums you got those files.
I tried to install twrp.img using flashy. Since flashy flashed twrp my kindle fire has been stuck on the logo screen. My kindle has no sd card slot and my PC doesn't detect in this state. Also the holding the power button tricks do nothing. What should I do?