Yellow Chevroned Parakeet Help!

[CaseyLei13]

Hi my name is Casey, I am the proud new owner of a Canary Winged BeeBee Parrot ( or Yellow-Chevroned Parakeet) named Rocky. He is extremely intelligent and apparently there's not allot of info out there on this particular Brotogeris' behavior or habits. So with that said, here are all of the really nice things he does:
*Absolutely LOVES apple and is learning to say it
* Very cuddly loves attention and scratchings
* Extremely smart, he is learning at light speed and retains everything
* He would rather be on my shoulder than anywhere else
* Shows allot of interest in his toys
* Is learning some basic clicker training and doing an excellent job

Now these are some things that I am having a little trouble with:
* He does not bite me territorialy but when he does not agree with something he will bite me and it is getting increasingly rough
* He seems to have seperation anxiety (I am trying to take him out for 1Hr 2x a day)
* He is completely happy in his cage for a while then all of a sudden he seems to throw a 'tantrum' , he bites on the bars repeatedly also chews on his own toenails!!!

I try not to reward ANY negative behavior, I do not yell at him or pull away fast when he bites me. I use a 'you get no attention from me' technique. If we are chatting nicely and he screams, I will turn my face and stop talking, if that doesn't work I will walk away. When he stops for a long pause I will say softly 'Quiet' and reward him with some apple. When he bites me we are usually trying to do 'step up', I don't yell at him or move quickly. But he is starting to bite me harder. He knows exactly what I am asking of him but he will only do it if he 'wants' to, so getting him BACK into his cage is hard and even apple won't do it.

I have allot of patience and time, so if anyone can help me have a happy, healthy, balanced parrot I would greatly appreciate it!
-Casey Lei