As you mentioned the DNS fails, I could see the following difference in DNS config:
set interface trust dhcp server option dns2 216.146.35.35
set interface trust dhcp server option dns3 208.67.222.222
The above two DNS IPs are missing from SSG 5's DHCP config. So please try including these as well.
Few other things that you could test are :
1. Try pinging gateway from the firewall.
2. Try pining DNS server IPs you see on the LAN Machines to verify the connectivity.
Sarab [ JNCIS-FWV , JNCIA-SEC , CCIP , CCSA ]
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