Feral definitely uses the damage now. Long ago, in BC and earlier, feral weapons had a "+feral attack power" that they used instead of the weapon damage.
The weapon damage does indeed affect your damage in cat form. You can easily test this yourself to see the effect. When you shift into cat form, your DPS changes, and when you try switching weapons, your DPS changes again.
It's useful but imo negligible. I would suggest 3 int
yes but it's hard to check only you have 2 exact weapons with different stats on it
How is +3 int going to be more than a negligible help to a feral druid?
It's debatable and in the end both are a negligible difference when playing feral
Imo it's a matter of preference