Thanks Martini and thanks lolsyb1982 for your comments, I appreciate them a lot. They give me some food for thought...
Some weeks ago when we started getting trouble with the NWs we slowly pushed backwards the BT, from 7:30 to the 8:30pm. We wanted to avoid those early WU and long NWs. We felt that they were caused due to being under tired. We compared how much our DS1 slept at the same age and he used to be at just 10-11 hours during the nights, and only slept 1 nap. Ideally we wanted that our DS2 slept from 8:30 pm to 7:30am (11 hours), whilst maintaining the 2 naps (2.5h in total). I must say that both naps take place in the kindergarten, so I have little control over them.
Regarding the night-feeds, we eliminated them already 2 months ago, and for a while we had no trouble. In fact we had excellent nights. During the last days (nights) we have tried lots of things, one of them giving him a bottle during the NWs and giving him extra food during the day. Most of the times he does no want it, but when he has drunk it, he still remained awake for a long time... So we guessed that this was not really the answer, but still we try it since we are a little bit desperate.
Tonight I am going to put him to sleep a little bit earlier, for example at 8, and check if this helps or not. He never has an issue to fall asleep once we follow the BT routine. I will also guide him to pick the pacifier himself, although I feel that what he craves is the contact with us, our touch over his face when we replug it.
You have asked me if something has changed recently... Well, lately DS is moving around a lot, trying to stand up and interacting more everyday. Constantly he is clapping his hands and trying to get our attention. He goes for the prohibited things like touching the tv, and looks at us with a smile. He is progressing. I wonder if his "improvements" cause him some kind of restless feelings. Also he is teething, but we give him some ibuprofen before BT.
I wish that we could know what was the answer to these Nws. When I talk to my work colleagues and friends, and they tell me that their babies (younger) are STTN, I cannot avoid to feel that it is my fault. I feel very guilty and hopeless. The only thing that I am sure of is that I do not want to try the Ferber (CIO) methods, but I am unsure about the rest.