Final scenario of adventure 4 has a villain which dings you for damage in between his two required checks.
Can you use hellfire lash to avoid the auto damage if you fail the first combat check and use its evade ability? (We ruled yes, the evade kicks in before the damage)
There is also a nasty Demon that takes a random boon from your hand and shuffles it into a location if you fail a Wisdom 12 roll. In this case we ruled that hellfire lash definitely CAN'T help you avoid that shuffling of a boon in because its evade kicks in after a failed combat check and the boon effect is before you act.
Related question, what happens if you have to shuffle a loot card into a location deck? Do you auto acquire it when you explore a location?
It sounds like everything you did is correct.
Related question, what happens if you have to shuffle a loot card into a location deck? Do you auto acquire it when you explore a location?
Yes, a loot card is automatically acquired when you encounter it. This is in the rulebook.