Hi,
1. Ah yes, I was also thinking that you were talking about points gains. For the use of the points to be restricted to only some categories, the ideal solution would be to have a generic solution to limit payment methods to categories of products. The problem with that is that you can't have several payment methods for different categories for an order so it's quite limiting because the system would then often display to the customer that he can't purchase finish the order because he has products from categories with different payment methods attached.
So no, there is no solution in that case with the options available. But it could be added quite easily to the user points payment plugin with a small modification of the code.
In the file plugins/hikashoppayment/userpoints/userpoints.php in the function onPaymentDisplay, you could add a check on the categories of the products (that you can find in the array $order->products). Just return before the call to parent::onPaymentDisplay($order, $ordered_methods, $usable_methods); when there is at least a product from a category for which you can't pay with points and that will remove all the user points payment methods from the selection of the payment methods.
2. I don't understand your question. In your hikauser_point_1.jpg I see a product on a listing of products. Where is the link with the points ? If you want to have that price displayed as untaxed, edit your menu item via the Joomla menu manager, and in the "products options" tab, turn off the "show taxed prices" setting.