You are exactly right, you need to add a Bool to your character called “AmIAlive?” and set it to true. When your character loses all their health (dies) set it to false. The Wolf is looking for this bool so it knows weather to chase and attack the enemy or to feed on the enemy. You will also need to adjust 2 services in the Behavior Tree.
In the BehaviorTree there is a Service called “Wolf_BTTService_IsEnemyAlive” (See Image)
There is also another Service called “Wolf_BTService_Is_DamagerAlive” (See Image)
In both these Services you will swap out the cast to character (to your character). That should be the only changes you need to make, let me know if it gives you any further issues. 
P.S. You also will want to add an “event any damage” node on your character to receive damage from the Wolf. You can see an example of this in the “BP_ShootingThirdPersonCharacter_EnemyTags” in the parent class folder.
Hope that helps