I don't think FFG is at fault here. They certainly leave a lot of wording "loose," but I don't think is one of those occasions. You just have to read it thoughtfully.
If no characters have poison, then all characters have 0 poison attachments. Which means all characters are TIED for having the most poison, and you can choose which character is attacked.
Crazy Cob does not engage the player when he attacks. The card would specify engagement if this were the case. There are plenty of enemies that attack from the staging area at this point. Attacking and engaging are only related in the following way: during combat, engaged enemies get 1 attack vs. the engaged player. There's no other rule that says enemies have to be engaged before they attack, so if a card says "enemy makes an immediate attack," they'll do it whether they are engaged or not, and do not need to engage as a prerequisite to the attack.