You didn't say what you used for boot, but I guess it is minirootXX.img. Use installXX.img or installXX.iso - I don't remember what is the difference between them or what is the purpose for each one, I didn't used them in years. Those images contain the sets and you can proceed with full disk install. Then, you can fix the firmware using the fw_update command, not the pkg_add if I recall correctly.
In the meantime, maybe someone more knowledgeable can give you some useful advice with minirootXX.img and firmware, if that is possible to install.
