In the above sketch (post #1) the cap C1 will add nothing to common mode filtering, but will improve DM filtering of the fundamental sw freq, due to the leakage L in the CM choke.
In the immed above it would be better to put your Ycaps by C13 and your CM choke immed after C13 for best CM performance, and make the Y caps 2n2 with a bead or 4E7 ( 1206) res in series with each for damping ...
Also C1 needs experimenting with size to get best CM noise reduction, again a damping resistor, say 10E may very well help with VHF ringing in this cap...
The tracks around the fuse are very long and will pick up noise, defeating any CM filtering ...