The DB didn't actually harm the tree, only "scared" it a bit.

If you choose to get the sapling, not the sap, Maurice convinces the tree to give a sapling instead. He is a devout Kynareth worshiper.

His quotes can be found here: Link

This is TES lore, Thorien. There's no right or wrong. Just theory and suspicions.

Spriggans where also friendly on the Knights of the Nine DLC quest line in Oblivion when you pass Kyne's trial. Non hostile also.

Also is annoying as hell... I wonder how Kynareth puts up with his rankings :P

Well, to put it short, since Y'ffre is the most powerful Ehlnofey, I think that the laws of nature that he established work all over Nirn, while his presence may be the most prominent in the Southern regions, in Skyrim, Cyrodiil, etc. it's still the same Y'ffre nature. Kynareth/Kyne, on the other hand, is not exactly about laws of nature, more about weather. She influences the weather which in turn influences the environment and that is more prominent in the Northern region, that's why Men worship Kynareth.

Good point, about the Crusader. I completely forgot about that. It´s when you aquire the Boots, right? 

This is curious. I know exactly one case of a non-hostile Spriggan in Skyrim...

I was going to relate to that. But due to my minimal experience with Oblivion, I didn't know much about the quest. Either than it had a black bear and spriggans.

Indeed