Hi,
1. There is no setting for that. To do that, you would have to edit the file "quantity" of the view "product" via the menu Display>Views and add the code:
if($this->row->product_quantity!=0)
before all the instances of the code
echo $this->cart->displayButton(JText::_('ADD_TO_WISHLIST'),'add',$this->params,$url,$wishlistAjax,'',@$this->row->product_max_per_order,1,'',false);
2. This probably means that you have several wishlist modules created and because of that, the system doesn't know which one to pick when add the product to the wishlist in AJAX. You have three potential solutions here:
- the best is to delete the wishlist modules that you're not using
- the second one is to configure all your wishlist modules in the same manner
- the third one is to turn off the "Use AJAX when possible for add to cart buttons" option of the configuration so that the full page is reloaded when you click on the button.
3. On which page ? Could you give a link and do a screenshot of the page ?