Why does the fvs318 firewall only pass 5gbps signal from a 30gbps signal line?

OK, I have setup a connection through a local cable ISP @30gbps and bypassing the built in wireless function in an Arris 860 modem. Unfortunately the ISP is in control of the Arris settings with that I requested the wireless function to be disabled so that no body enter my network through a back door so to speak. Also added a E1200 wireles 300 n 4 port router and single connection to a FVS318 Firewall router with the E1200 & FSV318 host settings changed. Meaning for example the Arris is for 192.168.3.1 and the E1200 would be something like 192.168.2.1 and FVS 318 would be 192.168.1.1 this way no router confusion and no router traffic collisions. With a dynamic ip from the isp. However, after configuring and connecting everything my speed throughput is great through the Arris= 30 for 30 and the same for the E1200 = 30 for 30. But after connecting some devices through the FVD318 firewall device the throughput speed was 5.25 gbps from a 30gbps line signal source. I could not find anything in the firewall router setup to change the throughput speed or how to increase or limit the speed functions. Please note the ethernet connection speeds are at 100mhz during the tests. Wireless connections are normal or no problems as of yet. My question is: has any body had this or a similar issue and if so: how did they fix the problem? This would be other than swapping out the FVS318 Firewall with another device.