Did you run the BT tool from DOS? If not, try again from DOS.
As for the dumped BIOS you flashes, you said modified? Was it an actual dump, modified, or a stock BIOS modified? If stock mod, then it would not contain the necessary NVRAM volumes were this change needs to take place, this would also cause error with the BT tool. If that's what you used, do you have a dump of your BIOS before you flashed anything else? If yes, please attach.
Also, flash "Entirely" not update means do not use Asus update tools, AFU, etc. you need to put on with a flash programmer. However, I know this is located in NVRAM, but stock BIOS does not contain both NVRAM volumes usually, so anything built from a stock BIOS is not going to work, you need actual dump from working system (that contains two populated NVRAM volumes).
I was only able to find one dump for this model at my usual location, and it's a stock dump not actual dump (user programmed or FPT'd in stock BIOS region, then dumped) so if you used same source (.com.br website .305 Bin BIOS) then this is not an actual proper dump. I cannot download the file they gave you at Viafix to check, but it may be from the same source (Upload for me here to compare, thanks).
We need to find actual proper dump, where person has not incorrectly done the above actions first. Your board may serve as this dump source, since it's from Asus, provided you have not flashed in a stock BIOS region using programmer or FPT. If you have not, please dump the BIOS region using programmer or FPT and upload for me to check.
If you do not have programmer, then use Intel ME System Tools V11 from this page in section "C" -
https://www.win-raid.com/t596f39-Intel-M...Tools.html
Inside you will find Flash Programming Tool folder, and inside that a win/win32 folder, select that win folder, hold shift and press right click, choose open command window here (Not power shell). Then run following command and zip and upload the created file for me to check
FPTw.exe -bios -d biosreg.bin