Well, you might get some different responses for those particular questions

I, for one, do say 'no bite' when my birds nip a bit too hard. I don't yell it, I just say it in a firm voice. If they are on my finger or hand when they bite, then I will do the earthquake thingie (tipping the hand
slightly, just enough for them to lose their balance).
As for the cage aggression...it is hard to say if it is just a stage or not. Could be, or it could be something your Quaker just prefers.
Now, I tend to not push the issue when my birds bite from the inside of their cage. It is their home after all

I have no problems using a perch to get them out. And they have no problems using one (and I'm a huge fan of stick/perch training because of this exact issue).
The thing to remember, when your bird is biting you from inside the cage or when he is on the outside...push gently into the bite. This, like the earthquake, tends to put them off balance. It is something that works really well for reducing the biting behavior.
Hopefully someone else will be along soon to give you some more ideas.