Long story short: I was bouncing between FIRMs, the one from 11.0 (when 3DSident said that I had kernel 2.51) and a corrupted FIRM (when 3DSident said that I had kernel 2.52)
All I had to do:
-f̶o̶l̶l̶o̶w̶ ̶t̶h̶e̶ ̶d̶a̶m̶n̶ ̶t̶r̶a̶i̶n̶
-Be on kernel 2.51
-Delete the FIRM112_OLD.bin nd the FIRM104_OLD.bin from the dgTool folder
-Put the FIRM110_OLD.bin and FIRM104_OLD.bin
-Start dgTool and downgrade to 10.4
And now 3DSident says that I have kernel 2.50-11.
All credit goes to
@Goombi as he managed to find the solution for this problem.