Thanks for the feedback, MVinter
So I guess you got an axle that is not Shimano standard thread (1.5 mm). I guess you did not get it form Peter then. There are 3 thread standard
1 mm, 1.5 mm and 1.75 mm. Too many.
And it's good to read that my headset problem is an isolated problem. But it looks like the rear brake line is a design problem, even though it was even worse on my frame where even the plastic guide was almost locked into the internal sleeve.
Anyway, I went for a 20k ride yesterday and the bike is fantastic. Eagle is now set precisely and I love it. Single chainring is so much better then 2x (no more mud in the FD, no anticipating on chainring switch). All 12 cogs shift easily, even the big one, just like the other ones. I appreciate the ability to adjust the reach on the shifter (the angle of the big shifter).
Then, geometry: as I mentioned previously, the short seat tube angle enables to clear the saddle when dropping the post. You can really move as much as you want. I went to a VERY steep short descent and felt safe as I could get my butt almost rubbing on the rear wheel w/o my balls knocking in the saddle
Then, The 2.8 Nobby Nic is great in the rear. Definitely better then the WTB TrailBlazer. I have climbed yesterday something I thought was an "impossible climb".
I forgot to talk about BB92. Surprisingly, I really like it. It really feels rock solid. Installing the BB was a piece of cake. To the point that I believe I could have pushed it gently with a mallet inside the frame. Pretty sure it would have been OK, but I already had the dedicated tool! Then, the Eagle cranks are nicely tight on the BB and compress some rubber caps that prevent mud/water from penetrating inside. I really like that design.
EDIT: Here is a picture of my ride yesterday, the one I posted on Strava