Hi man,
I am not an expert but I had the same problem than yours: the Nat type plus I couldn't play with my other lebanese friends plus it took a little bit of time to find Fifa matches or Uncharted games for example. So I discovered the DMZ method online and I am sharing you my little knowledge.
First, I have WISE and an old modem with not even a brand name but not bad in port things so I will tell you what I did to DMZ my PS3.
So ------->>> To DMZ your PS3, you must go to the NAT section of your modem (I advise you the D-Link one) and you choose an ip address to assign it as a DMZ host for example my default gateway ip is 192.168.16.1 so I chose the DMZ one 192.168.16.34
So, even if you can't find your PS3, assign a DMZ host then after doing it reboot your modem.
After it, configure your PS3 (custom setting not easy) by giving it the IP you put as a DMZ host. (I hope you know how to do it on your PS3 and you can see on Google nothing hard)
Turn off PS3 and turn on.
I hope it helped.