questions

1. where do the people who work for candy man meet and organize?
2. what secret codes or signs does the candy man use in the city?
3. who would know the identity of the candy man or other high ups in the organization?

1/ There's a few small, divided cells that operate independently of each other, managed by Cornelius Blockbuster. The one this assassin belonged to worked out of a small storage building next to a warehouse on the edge of Bishop's Markets, somewhere between Blackhive Meadery and the edge of the Blackbaron College of Esoterics.
2/ There are symbols inscribed on shops and buildings with an ink that can only be seen wearing special enchanted glasses, indicating black market contacts - and even then they don't glow or anything so you'd have to be looking for them and know what they mean. Candyman isn't the only one who uses these symbols -they're a commonality in the underworld here. You're told what the symbols for 'fence', 'arms dealer', 'safe haven' and 'contacts' are. As for codes, anything written between members is ciphered, with the code changing monthly. You learn this month's code.
3/ Blockbuster would, and MAYBE Father Bones, but maybe not. Blockbuster himself carries a poison intended for self-termination if ever caught by the authorities.