The issues you raised have now been fixed.
As it is open-world, there are two things I noticed when playing the mod:
1. The player is searching for keys wandering the various levels; or
2. The player has several keys and is looking for locks to use them.
Prove your mastery of air = the ethereal blade. It's cryptic on purpose, because that area below is a bonus
You need to search the world as it is not linear. Swim, climb high, and look closely at the vegetation, especially in Wanderer Heights.
Keep an eye OFF the prize as the weapons, armour, and other bonuses sometimes disguise what you should be doing, or where you should be going.
I don't mean waste your time analyse every tree or area, but search generally.
Wanderer Heights and Artak's Dungeon are where you'll open the mod to explore more.
You'll need to acquire the green gem to enter Copseville too.
Check the Wanderer Heights Burial Ground to acquire the quest item.
I'm sorry that you're finding it frustrating.
I do not like mods that make the player stuck, which is why I changed both my mods to prevent this.