[Info] Miscellaneous Attack Detection Settings

Is “packet checksum verification” the same as “stateful packet inspection”? If there is a difference, what is it?

No they are not the same.
Checksum might slow your conection but try it if you want

What is Stateful Packet Inspection? When an IP packet arrives at the firewall from the Internet, the firewall must decide if it should be forwarded to the internal network. In order to accomplish this the firewall "looks" to see what connections have been opened from the inside of the network to the Internet. If there is a connection open that applies to the packet that has arrived from the Internet then it will be allowed through, otherwise it will be rejected.

Hope this helps