The SSL500 & x550e/x750e/x1250e are all the same hardware. I wrote the HexHound article and while the screenshots are from an SSL500, I also have a x750e. That said, your BIOS does look different and I would proceed with a extreme caution. Unless you find someone that has the same BIOS as you, and flashed with success, I would suggest using a PCI-e video card and entering the BIOS that way. The BIOS flash is only necessary to redirect BIOS output through the null modem at boot. If you can change the settings blind or use a video card, it will work perfectly fine. IIRC, a VGA header is also on the board but it's an oddball size. Nevertheless, it's another option if you want to go that route.
PM me with your e-mail address. I have a dump of the factory image I can send you (but I have to find it!)