OK, let's start this from the top. Do you have your original NAND dump? If yes, then write it back. Once your console boots up, update it to 7371 by placing the 7371's $SystemUpdate folder on a USB Drive. Once updated, dump your NAND again. From now on, this new NAND dump will act as your original NAND image for further use. Make sure that you have the correct CPU Key by decrypting your newly dumped NAND image in 360 Flash Dump Tool.
Now, use the latest Jtag Tool to create a freeBOOT v0.4 image for your console using your CPU Key. Then make sure that it has the correct 6BL[CF] and 7BL[CG] i.e. 12611. Also check whether it gets decrypted using your CPU Key. If everything seems fine, write this new freeBOOT v0.4 image to your console, do a power cycle, then turn your console on. Hopefully, you will be greeted with the Welcome screen.