Here's a quick but in detail information on firewall topology and best practices. Also, don't forget to checkout our firewall resource center.
Your design does not meet any security standards, as one of the major factors is the single point of failure. There is no internal firewall to protect the internal/private network. The router in between will not be able to protect anything if the firewall gets compromised and it will open up the doors for attack. I would suggest you go through the above resources to get a good understanding of the design principles. Once you understand the principles you will be able to identify the problems and rectify them accordingly.
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