You need to complete all of the following to get 100% Total Synchronization. You can check your progress from the Main Menu - Progression Log - Progress Tracker.Story
You do not need 100% Perks, 100% Skills, 100% Tools crafted or 100% Gear crafted.
To Frighten 15 enemies for the Fight Club challenge, use Spikes on Brutes and Fear Bombs on everyone else. I recommend upgrading your Spikes and Fear Bombs beforehand.
You can buy treasure maps from any Shop for £5000 each, that show the locations of all the Chests, Locked Chests and Illustrations in Whitechapel and City of London.
I was stuck on 2 Helix Glitches in the City of London. There is one between two chimneys in the south west corner, near Temple Church. Here is a video by forzatalje showing how to get it, at 6:25
There is another one that is actually outside the City of London, in the Thames which is why it doesn't appear on the map. You will come across the location during Memory 5.