I am sorry to tell you that your horse is MAJORLY disrespecting you! His behavior is very agressive and DANGEROUS. Personally, I would recommend getting a professional trainer. 6 months is plenty long enough for your horse to become adjusted to his new place, and working him 2-3 times a week is really ok. I mean, truly, who honestly has the time to work thier horses everyday. Horses are intellegent animals who can retain their lessons. After the trainer has worked with him for a couple of months, you should be able to pick up where they left off.
If you are against getting a trainer, then I would invest in Clinton Anderson's roundpenning for respect tapes or dvd's. Watch them carefully. He has the belief that you should be as gentle as possible, but as firm as necessary. Be very careful. Wear a helmet and take a whip with you. Use it if necessary. I don't believe in abusing a horse, but I believe less in them harming you. You CAN NOT hurt a horse with a lunge whip. All you will be telling it is that you mean Business. Watch horses out in the pasture. They will kick and bite each other. These are 1000lb animals. Do you really think that you could hurt them with only your hands or a longe whip? I don't think so.
Right now, he believes that he is above you in the pecking order. That is why he pins his ears back when you approach him if he's eating. He needs to learn that YOU are the leader. I can approach any of my horses at any time (I have over 20+ horses) and do anything with them I want to. I could take their food away while they're eating it and they would do nothing, Why? Not because I am mean, or beat them or anything like that. Because I am the leadmare and they respect me. It's all in the attitude. Good luck and stay safe.