Need enhancements to this plugin

While this plugin works well, it needs lot of improvements. Here is the biggest flaw that I found.

The biggest bug of all is, I have restricted the gift based on amount and product category however when people add other product categories, it gives the gift. For example, I sell Clarified Butter & Edible oil at my website https://gheestore.in
I have restricted Minimum order value and to certain Product categories however when people add product outside of the product category even for a single penny, it calculates the gift for the total cart.

If you have time visit my website and add 15KG tin packs, you will not be offered any gift but the moment you add any simple product, it calculates gift for the whole cart value.

Please fix this immediately.