This should be your first stop.
Core2 Overclocking Guidehttp://www.tomshardware.co.uk/forum/259899-11-core-overclocking-guide
Shadow's Gigabyte motherboard OC guide:http://www.tomshardware.co.uk/forum/page-245679_11_0.html
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar.
You are doing not badly. Change your memory voltage to factory recommended values. Change your memory multiplier to 2.0. Core2 systems really do not benefit from overclocking memory.
Using the stock cooler, you are going to bump into thermal limits long before you reach the maximum recommended CPU voltage of 1.45 volts.