Your DNS resolution is not working. The tunnel is set up fine.
You need to make your router listen for DNS forwarding on vtun0. When you say it didn't work, do you mean you got an error when typing the command, or that you typed the command and committed the change but still don't have access?
If the former, Did you type configure before issuing the command?
configure set service dns forwarding listen-on vtun0 commit save exit exit
If you successfully committed the change, then the problem is with your DNS server. I'm unfamiliar with the name-server directive, but I'd check that your DNS server at 192.168.1.100 is configured to accept requests from 192.168.100.0/24. Also, let's make sure that your router is forwarding DNS correctly - can you post the results of show service dns forwarding?
Leave the redirect-gateway line in, unless you don't want all traffic redirected through the tunnel.
