>We are able to track down and physically explain (thanks to MRI) the sentation, the objective part of consciousness (Chalmers's 'easy problems of consciousness'). That really exist and we can prove it (or we have an idea about experiments to run to prove it)

What we prove is an evidence that is filtered through our sensory faculties and experienced by our minds. Our minds still remain judge, jury and executioner and in this same sense if we are to take seriously the faculties of our minds in assessing the physical world, then we must also take seriously our experience of conciousness which remains even when we are unable to sense the physical world. In this sense our experience of conciousness is more real than our looking at an MRI.

>then we do not need to think subjective experience really exist.

What would follow is that you do not need to think subjective experiences exist for others, but for you to make this assessment you at least must have a subjective experience.