Drupal Commerce "add to cart" form with complicated attributes
The biggest problem is that the Drupal Commerce module adds to cart
  products with different attributes as a single product.


Have you tried unchecking the option to: "Attempt to combine like products on the same line item in the cart."

It's on the "Add to cart" product reference field formatter settings on the product display content type

e.g: admin/structure/types/manage/product-display/display