After many tests and tweaks, it seems that I have managed to leave it stable at 9-9-9-24 2N@2000Mhz.
I was advised to touch some voltages (QPI, IOH, ICH and CPU PLL apart from increasing the RAM voltage a little more to take into account the Vdrop that my motherboard has) and it works perfectly.
12 hours of prime95 and more than one memtest later, the computer is working perfectly. At 4.2, after several hours of prime, it does not exceed 75º.

By the way, having it stable, I tried to increase the latencies to check the performance with different latencies at 2000Mhz and the truth is that there was hardly any difference in synthetic tests, so I imagine that in everyday use it won't even be noticeable.

Best regards and thanks!!!