that is about all you can do , the TCP/APN settings, etc.
Now, also know that Opera Mini can be finicky... it might not connect for today and just up and work tomorrow or the next, out of the blue. So don't give up yet.
After installing OM, did you remove the battery (while powered on) hold for 30 seconds, replace and reboot? Do that every 3-4 hours until it starts working... might help. And there is NO guarantee that OM will work, but it should.