I just installed the firmware with latest PMC (300.2.11.1015) and for now everything seems to work properly.
But I have a new question about that. When I update the bios, there is a CSME FW integrated into the OEM bios. I noticed with ME Analyzer, at the "OEM RSA" line, by analysing the OEM bios and the last CSME update that I just do, there is two differents values. There is "Yes" for OEM Bios and "No" with the file you provided.
So, by updating the CSME as I just did, with "external" merged files, do I lose specificities / features or something else compared to an update that would come directly from the OEM bios ?
Ah, perfect. So it was definitely a bad PMC firmware by Intel. Thank you for doing the test SabriLLe. 
As for your question, the difference is normal. Make sure to read the Firmware Regions (RGN/EXTR) and Firmware Configuration (CODE/DATA) paragraphs at Section B of the CSME thread.
I had read this section, from what I understood, the DATA section of FW configuration may be in different state, Unconfigured if he’s “empty” or Configured if the OEM applies his setting.
In the case, that means the CSME FW that you provided is Unconfigured and the one in OEM bios is configured.
So, is there a way to fully configure an untouched CSME FW with FIT, to inject all specificities / settings already existing in the CSME FW present in OEM Bios as if it was the OEM who configured it ?
Or may be the opposite, simply inject new CSME merged file (that you provided) or separely files (CSME+PMC) in the OEM Bios open in FIT, build the BIOS with this files and flash the system ?
I had read the clean dumped guide but it seems that is only to clean an EXTR FW Initialized by OEM.
FWUpdate deals only with CODE, not DATA. The DATA which is already flashed on the system remains intact after FWUpdate. Thus FWUpdate does not need an input image which is configured. Whether you input a RGN or EXTR or dirty EXTR (+ PMC for CSME 12) does not matter for FWUpdate. It is all the same to it.
FWUpdate is the easy way to update the CSME firmware. But if someone wants to manually update it then they would need to re-write the Engine region of the SPI chip which requires read/write access there (unlocked Flash Descriptor) and the use of a general flasher such as Flash Programming Tool, flashrom, hardware programmer etc. The same applies when someone wants to repair the firmware or transfer it from another identical model. The CleanUp Guide is normally used for latter. However, you can use it if you want to update the CSME firmware of the SPI/BIOS image proved by the OEM as well (to be flashed via a programmer, FPT, flashrom etc), it works just fine.
In your case, we wanted to downgrade the CSME firmware but the Version Control Number (VCN) was violated so FWUpdate was not an option. However, you have an unlocked FD (rare, should normally be locked per Intel recommendation). So we used FPT to re-flash the Engine region of the SPI/BIOS chip using the one from the OEM’s equivalent image file.