The great thing about sniffing the area for yourself is when you do find truffles the scent will stand out from the familiar dirt smell. It also keeps the dog engaged with you whilst you check. If you feel the dog is over enthusiastic you could teach it a behaviour that is associated with your movement to bend down and sniff the ground. Wolfy doesn’t look this type of dog, but just an idea of how to add a behaviour associated with this movement.
The earth looked quite rocky where you were, and hard to dig. Putting the tin into the hole for him to find was spot on.
You mentioned that you had lots of breaks. What is the current searching time for Wolfy? What are the signs that you decide that a break should be taken?