I think I have all the components, but it doesn't work. I put them on the table (thyrm extract, spider web, wood, some broken weapons for iron, belladonna plant and ONE diamond, i could find only one in those holes in the ground...) and go talk to Oswald, but he keeps giving me the "I'll be back when I get the components..." option! What am I doing wrong? Are these the right components? What about the "two" diamonds? Help... Thanks!

Just explore the areas to the east until you find another diamond. There are other area maps accessible than the one where you crashed.

You can buy another diamond from a merchant you'll soon rescue from the areas outside the Ice Temple, if you get desperate. However, you should find a diamond in Oswald's ship somewhere, I believe. It's one of the first things I found after his ship crashed. Did you thoroughly search the crashed airship?

There is indeed a diamond in the ship - just played through that part of the game again. But if for some reason you can't find it there, one will become available in the next area to the east, as mentioned before.
EDIT: Don't forget to press your ALT key while you're in the airship to see ground items and containers highlighted. There are several places to look.

IIRC there is also a diamond available within the treasure cache in the eastern part of Andora.