If your dump is good. Then you can not downgrade that model.
What is your datecode? Has it ever been refurbished?
You may be able to do this
EDIT - I looked at your dump, and it looks like it is:
CECH-25xx (JTP-001) with 3.56 from factory - datecode 1A (rare)
CECH-25xx (JSD-001) with 3.56 from factory - datecode 1B (common)
CECH-25xx (JTP-001) with 3.56 from factory - datecode 1B (common) E9 60 0E 92 2F5F0 2F 5B 2F 5B (RLOD+)poweroff @ downgrade 355
(3.56+ + spkg fix + signed 3.55 priv : should work) 3.56