Change volume size in header to see the structure better (your bios itself doesn’t care about this):
Looks like
Check Flash Map when done, this is the reference for finding the correct address for this kind of bios:
See last line 48 00 17 is address for first microcode, absolute address would be start address of bios region + relative address => 18 00 00 + 17 00 48 = 2F 00 48 for 1st microcde