TegraRCMSmash comes with a 32 and 64 bit version from this
site. Have you tried both?
Use the homebrew application
ChoiDujourNX to update your firmware without burning fuses. Fuses are designed to prevent you from downgrading. It prevents fuses from being burnt by enabling AutoRCM. AutoRCM is a type of brick in that it AUTOmatically boots your console into RCM as the name implies. This means without a way to send a payload, the console is bricked. However this can be advantageous in booting into RCM without the need for a jig. The reason it prevents fuses from being burnt is because the console's normal bootloader checks the fuse count with the current firmware version (think of the normal bootloader as the Nintendo logo you see during startup). Custom bootloaders bypass this fuse check. Custom bootloaders are also the ones that boot CFW such as Atmosphere or ReiNX. And the reason you may wish to downgrade is in case a better exploit is released on a lower firmware such as a hypothetical untethered coldboot hack. As for which firmware you should upgrade to, I recommend any of the 8.X firmware versions as 7.X has a nasty USB bug.
Sept is a payload that is required for booting firmware versions higher than 6.2. Free CFW come with this payload when you download them. The usage of sept results in an extra splash screen when booting up the console via CFW. Make sure you update your CFW before updating your firmware with ChoiDujourNX.
The latest update is sufficient.