Can't you only stealth from any single person once? How do you do reset/thievery?
You can reset the counter if you delete/fire one char and just create a new one for free. Put 3-5 points in thievery and rob the merchant again. Delete the char afterwards and higher a new one, repeat this as many times as you like.
That's btw the reason why Ellezard has this much epic gear on every char.
It's just exploiting the game and bragging afterwards. Everyone can do it this way and it makes tactician for sure easy but it is not intended. You can even reload every time until you get the dreamgear you want on the merchant.