What do I do when the blood trail ends in the center of the five luminated mushrooms?
You probably lost the trail. Go back to the last place you saw the blood trail and try to find where it continues.
There are some freaky trees in the final area which look a lot different than normal trees, do they come alive? And if so, can you kill them?
Is Garrett a lumberjack? If you think so, give it a try... after saving the game to a separate save slot.
If you've read "Lord of the Rings", these Trees might be familiar... and yes, they do come alive.
I seem to be missing a lot of loot, is there a big stash somewhere?
There is loot all over the place in the "season caverns", on the rocks, etc. Mainly silver nuggets and gold nuggets, which blend perfectly into the stone background they're lying upon.
With the patch, the loot became more obvious: Now the goodies are not stuck so nicely into the rocks no more, but lie on the floor next to the grey rocks.