I am adding pictures of the open leaves and of the color and clarity of the tea 'soup'. See below and above. That's why I just tasted my 2004 again, and decided to apply the advices I wrote.
And what a good surprise to see (taste) that my advices are working! Today, I took my time to flake the cake leave by leave. I think I didn't break any leave today, as opposed to Tuesday when I was so excited to taste from it. I also reduced the amount of dry leaves, which are so full of vigour. What I didn't change is the water that had just reached the boiling point. (I remain true to my tea master's teachings not to use lower temperature water to reduce the bitterness).
The result is a pleasant young pu er flower bouquet with some smoked wood smell and a little bitterness behind all that. I am amazed at how the bitterness dramatically dininished. The careful flaking did the trick. It worked so well, I think I shall use a few more unbroken leaves next time.