First, let me confirm iNano is correct on all accounts, and just elaborate a little on them. The difference between Knockdown and Stun is purely when they go away. Both are incapacitate effects, but Stun goes away at the end of its Action Phase, while Knockdown goes away at the beginning of its Action Phase (or at the end of the round). This means that Knockdown will never deny a creature from taking an action, but it is still useful for the other Incapacitate effects like iNano listed.
Invisible creatures can't be targeted. They can still be affected by zone attacks/effects, damage barriers, and counterstrikes though. So there are ways around the Invisible trait, even if it were to be permanent...
Because the official card database isn't up to date, some cards can not be inserted into a forum post.
Now, to the question that iNano missed. The latest supplement update answers this question on page 9 in the Effects section. If an effect grants you an ability with a limited number of uses, those uses are tracked by the source of the effect. Which means, if you move an enchantment to a different target, it does not regain any uses of its ability. Reading the Steal Enchantment card, it does say that you are just moving the enchantment and switching control. You are not recasting it (though you do have to pay the mana cost "as if" you were casting/revealing it for the new target).