what dongle are you using? i may can help you find the correct hex for your dongle.
i see you have a cobra usb dongle... you should be able to use that to get into FSM easily on 3.55 just use the correct psgrade
copied from psx-scene
Factory Service Mode
Factory Service Mode is used to perform operations like downgrade. (and remarry bluray)
To enter factory service mode using Cobra, follow these instructions.
Power off your PS3.
Insert Cobra USB in the PS3. Make sure that it is in factory service mode (switch in right position).
Turn on PS3 and press eject quickly.
Blue and green led’s of Cobra will flash while booting, green led will be the final led on success. If you are on a regular ofw or cfw, the console will shut down. If you are on cobra CFW, the console will continue booting normally (unless it is semibricked, in that case it will stay on forever). In both cases, don’t worry, despite that, the PS3 flag that sets factory service mode will have been written, just shutdown your PS3 manually and next time you will be in factory service mode.
You are now in factory service mode. Don’t connect Cobra USB while in factory service mode. You can find tutorials on the internet to perform operations like downgrade, exiting factory service mode, etc.