1. The application for the design patent can be approved with great certainty. Of course, you can sue the other party for infringement after authorization.
2. The amount of compensation depends on the evidence, which can be the loss you suffered because of the other party's infringement, or the gain the other party got because of using your patent packaging fraudulently.
3. For infringement, Zhang San is the seller of infringing products, and Guangzhou manufacturer is the manufacturer (if it is your patented packaging, not just toilet paper), both of them can be defendants.
4. For the products of Guangzhou manufacturers, you have no reason to apply for other people's patents, only legal; In practice, even if you apply for a patent, you will be authorized.
But because the patent you applied for has been sold before the application, that is, it has been publicly used, so Zhang Sanhe and Guangzhou manufacturers can prove that your patent is invalid. On legal issues, speak with evidence. If the evidence is conclusive, your chances of winning the case are slim.
6. If your packaging is graphics/patterns (because you applied for a design patent, it should be drawings), it also meets the protection standards of copyright law. Copyright protects the rights of graphic designers, which are automatically obtained, so they can be sued for infringing the copyright of product packaging.
7. In addition, the other party's unauthorized use of your product packaging actually violates the provisions of the Anti-Unfair Competition Law, and can also sue the other party for unfair competition.
8. If you go to court, in order to improve the chances of winning, it is best to find someone who understands intellectual property rights, not just patents or civil lawsuits.