Good work fixing the DPC latency issues, sometimes a re-install is the best way to go.
For your BIOS update, you need to confirm your motherboard model, and the motherboard download website.
BIOS has nothing to do with the OS 32bit/64bit version, it will install for both versions.
D/L the USB flash drive version, this is the best way to update your BIOS. Gigabyte "How To ~ Qflash Guide"
Go to the "Flashing With Qflash" section.
Use the Qflash method with a USB flash drive formatted to FAT32.