fx3000se wrote:but thats a 1.2GB file! This can impossibly be the fastboot ROM part only... ?
Sure. Fastboot Roms contain more files than just normal ZIP update ROMs. Further they are stored with another compression.
Flashing fastboot Roms is allways the best way to completely reflash your phone in clean way. after that you can start again with unlocking bottloader and flashing custom roms.