I'll address the clipping thing first;
"Your other bird may not have been a brat, this little guy is sure developing into one & needs to be slowed down.....if he were mine, I would start with clipping his wings, that often takes some of the bluster out of their sails, plus the wings will grow back with his first molt.....which may only be in a few months, so time may be of the essence....."
Not everyone is a fan of wing clipping and it puts a real bee in my bonnet when people suggest wing clipping when they're still so young. Vital muscle development is still happening at this point in their lives and so to take that flight and development from them, in my opinion, is just wrong. Teach him manners regarding food and behaviour and if still nothing has worked then AFTER his first moult and he's confident with his flight, consider clipping if his attitude hasn't changed.
"cage aggression, displaying aggressive and territorial body language/He will do it with toys."
So it's not just FOOD aggression then?
Yes, it's very very common.
Merlin is VERY cage territorial and I cannot change his food or toys without an attack 90% of the time. My partner has to do it because Merlin tolerates him being in his cage better than I; he also deals with bites much better than me. Merlin has been like this for pretty much as long as I can remember (he's 2 now), he had a few weeks of being an angel then he got into a routine and found out what was 'his' and what wasn't... and become fiercely protective of what is his. We have stopped actively discouraging it because everything we have done has not curbed his aggression - and we have tried everything, from the polite "No biting sweetie" to the more frowned upon things that I won't recommend. We always tell him "No Merlin" if he does bite, but basically we've made adjustments to our routine and life which means we get bit less and Merlin gets less anxious about his territory being invaded.
Merlin will eat out of our hands, off our plates(!), from his dish in our hands etc. But he would also snap at our fingers sometimes whilst feeding like that. (Sharing privileges of our yummy food then go to shot for a while.) We have found that keeping Merlin to eating from HIS dishes, in HIS cage, is the only way we've been able to combat his possessiveness over toys and food when outside of the cage. He'll still grumble, but a "HEY" from us usually puts him in his place.
So basically, my recommendation is; he doesn't get fed on his playstand, he gets fed in his cage. If he's cranky because he's hungry, plonk him in his cage near his dish. If he's grumbling at you because you're eating something that he wants, plonk him in his cage near his dish. If he lunges at you when he's on his playstand, "No!", give him a moment, then walk by again. If he lunges again, plonk him in his cage. If he does a scream at you because you're touching his toys, try again, if you get bit, plonk him in his cage.
The pattern I'm trying to get across here is that it's HIS cage, which I think he's more than entitled to be possessive of (I'm sure you hated it when parents came in your bedroom and started rummaging around for no good reason), and if he wants to have a tantrum about something or other, he can go to it and have it there. If Merlins being a pain in the butt throwing hissy's all night long, he goes in his cage and before long he's at the bottom ringing his bell asking to come out again, where he'll be a real sweetheart because he wants to be out and playing with mommy/daddy.
You baby needs to learn that the behaviour is NOT okay and will result in being caged. Merlin doesn't see his cage as a punishment (which it might seem like it is in this post) but as a time out - a break from being anxious or stressed about people touching his stuff. He gets to be in his cage, with his stuff, with his food, with bars stopping you from getting to it. Sometimes birds just need that safe space.
You said your breeder noticed no aggression/dominance, your bird was weeks old at the time, new flock, new surroundings, new everything - he's going to change.
I think a lot of people get anxious and uptight about parrot behaviour without understanding that your baby, hand reared or not, is still not a domesticated animal and they have pretty much all the traits and qualities of their ancestors.
So please bare in mind that parrots arn't really domesticated. If you've ever seen an aviary full of birds, or a documentary, you'll see birds scrap with each other for who gets the rights to food first etc. It's natural for him to feel hostile towards people coming near his precious resources, whether that's his bedding down area, his food or his mate. I'm not saying to encourage it, just don't view your bird as a "bad bird" because he's doing this. It could well just be a phase he's going through; you're doing right by him and he might grow out of it, or he might not. Merlin is 2 now and although he was doing well with the biting at first (I would go in his cage) he got worse and now I won't try to go in his cage.
If all else fails with your ignoring/eye contact and stern 'no's/caing, you'll just have to accept you have a bird who is not a fan of sharing his food/toys. This just means that feeding times are restricted, he's caged when you eat, you invest in a cage with swing out feeder doors, you buy toys that don't need to you be right near his beak when playing together, etc. I've got a ton of scars over my hands from Merlin and his inability to share; it's something we accept and deal with.
Sorry for the long post, hope it was somewhat helpful...
just my thoughts, some other members should definitely have some other suggestions
