The "WAN" configuration of your Internet box is on the ISP's side, the Internet side of the box. Your computer however is on the "LAN" side, aka the home side of the box.
Now, the default Gateway and DNS settings are two things completely different.
Default Gateway (also called router): the device a computer will ask when it tries to reach a computer on another network. Think of it as a door in a wall. The rooms are the networks, the door is the router. It has two labels, one on each side (one IP address per network it is connected to).
On your side, the box has an IP of
192.168.1.1 and on your ISP's side, it has the "WAN IP Address" in your WAN status screen . Note that IPs on your side of the box are local, as such, they can't be seen from the outside.
The gateway in WAN status is the door that allows your box to see outside of your ISP's network.
DNS (short for Domain Name Services): The system that allows your computer to translate a human readable name (like
superuser.com) into a machine-understandable IP address (like
126.96.36.199). Now, in most home network configurations, the DNS server used is the ISP's DNS server. On most recent boxes, the box itself acts as a DNS intermediate, which is why it sets itself as your DNS.
The fact that you can't access Speedtest is most likely a DNS problem. Contact your ISP or use another DNS.
As for your port forwarding issue, here's what you have to do:
Set up the port forwarding: any outside port to port 22 on your PC's local IP
From the outside, connect to your box's WAN IP (as seen in WAN status screen) on the "outside port" you choose when setting up port forwarding. Don't use the computer's local IP.