Well, the teething is over and I made some experiments, so:
- his 5:40 habitual waking is no more, now his wake up time changes with the bedtime
- he still sleeps almost exactly 10 hours every night, no matter how early or late I put him to bed, but since he is in a good mood whole day, then I guess it's just the way he is. I extended his first activity till 4 hours, and I keep his daytime sleep up to 3 - 3:15 hours altogether, so he ain't got the possibility of compensating during the day, and still he is in a good mood.
So I just have to make sure his bedtime is around 20 or 20:30 (assuming it will not overtire him) and then I get to sleep till 6-6:30 which is acceptable.
Since the teething he started some night wakings, 3 or 4 every night, but its enough to put the pacifier in his mouth and he goes to sleep. This week I will stop using the pacifier at all, hopefully those wakings will stop then.
All in all, now I at least have a feeling I know what's happening and can adjust to it, so it's good.
Thank you very much for all the advices!
You are doing a great job, its wonderful, that one has someone to ask in a time of doubt and lack of ideas, what to do next.