correct me if i am wrong

1. portforwarding is used so that outside computers can access your computer. most common use is for p2p and hosting games. does not affect net speed
2. port number is the port used in portforwarding. decided by whatever software you need to forward. eg. warcraft 3 you'll need to forward 6112/6113 if you want to host games
3. dmz is part of the network that is not protected by firewall. generally you dont put any computer there.

conclusion, if you are having slow browsing speed, none of these options will matter. if you are having good browsing speed but bad p2p speed, you need to do some portfowarding.