Just be patient, it took my ecky a couple of months before she was comfortable with me and even longer before she'd take any treats. Just sit near the cage as often as you can talking to him, eating your dinner, watching TV whatever you're doing that requires you to sit. While he is skittish with you keep the door closed so he doesn't fly off. Over time he'lll realise you're not a threat and setllte down - be aware this may be months, when he is calmer with you have the door open.
I know this is a touchy topic but you could try clipping his wings, some guardians have found thier birds have settled quite a bit and have made a lot of progress by the time the feathers grow again. This is really a personal decision and I don't mean it to start another debate - just a suggestion.
Also try a treat that he doesn't get in his dish everyday. I don't give my girls sunflower seeds in thier everyday diet, only by hand so they are a real treat.