Greets!

I also have had issues with PHP and nginx but on a Raspberry PI flavor board and I found this link to be helpful in getting it up and running with a MySQL database and Zabbix system monitoring a time ago.

You of course will have to adapt it to the Omega environment but it may give you some ideas of how or what you may have missed.

Setting up PHP, Nginx and FastCGI

Good Luck!
~Icky