[Note: For an example of Valyrian steel used for something other than a weapon, see the passing mention of Aegon the Conqueror's crown here]

How was Valyrian Steel thought of? Was it considered as precious before the Doom as it is "now"? Did they ever make non-weapons out of it (e.g. forks, jewelry, etc.)?

Valyrian steel was always costly, but it became considerably more so when there was no more Valyria, and the secret of its making were lost.

Mostly it was used for weapons, but there are undoubtedly a few items like those you mention floating about.

How do you feel about "twist endings"? Is this a sign of a weak storyline or effective sometimes?

Depends on the story.