Thanks for making such progress on a routing engine for cycling! I want to call a few OSM features to your attention. The tag highway=living street designates roads where cyclists (and pedestrians) have right-of-way over motor vehicles, and so are much safer. Similarly, motor_vehicle=destination implies access restrictions that give much lighter motor vehicle traffic, so I believe these roads should also get priority.
These features may already be implemented, and just weighted lighter than I would prefer. I figured I would check, since they don't seem to count as 'traffic-free' in the routing summary.