@arpenteur I think C3D is not using the breaklines you added. I have a tool that lists information about objects, including if they are being used as a breakline, and which surface it is used in. I am not getting any linework to show up with such information in your drawing, until I add just one featureline as a breakline in a new breakline set. Looking at the 100+ breaklines you've added (first, that is a lot for a single set, better off making multiple sets) there are many with just 1 vertice, and many more with just 2.
I suggest just adding just a few breaklines to start, the centerline and edge of pavement featurelines. Also, be sure to use the Supplemental and Weeding factors. I would suggest 20 and 0.2 for these settings.