Regarding the last part - I thought she used an ordinary gold coin dipped in poison, slipped into the insurance salesman's customer's bag of gold? She'd earlier observed that the insurer bit all gold coins he was paid, to make sure they really were gold - so he died of what looked like natural causes, long after Arya had left the scene. Simply
hoping someone dies of fright doesn't sound like a good plan; worse, the client might see iron coin before paying and think
he was the target; and worse still, a rare, reliably-deathly-terrifying iron coin would remain at the scene for anyone to take —
user568458 23 mins ago