First, try a low speed simple USB 2.0 stick with 8 Gb capacity, maybe you just have a controller incompatibility.
To flash dsanke modified BIOS you have to do that hardware mod, short these 2 contacts to remove Asus bios lock. Are you sure you did it right?
Or you can remove bios lock with software method as described here: https://www.win-raid.com/t3908f16-GUIDE-Grub-Fix-Intel-FPT-Error-or-BIOS-Lock-Asus-Other-Mod-BIOS-Flash.html
The bios lock is located at 0x939.
Or, you could ask that Lost_N_BIOS guy, make a thread and ask for help with 2402 modification.
Or, you can take 2301 unlocked version here:
P.S. Could you please share that latest dsanke 2402 version? Download links not working.