So...I have read the OP's original post and a few following it but I haven't read everyone else's comments, please forgive me if I repeat anything.
I don't believe this bird is an early bloomer and going through puberty.
I see that the bird has made some progress and is biting less.
I dont believe this bird wasn't fledged because I have one of those special...oh so special birds and this case doesn't remind me if him at all.
I do think it was or is a combination or sudden cage aggression and too much junk/sugar from the fruit ext and perhaps the fact you got another bird and Navi could have decided that they like the other bird more than you. This can happen even if the 2 birds don't spend a lot of time together. I gave 4 Conures, my 2 boys are close friends despite the fact the don't share a cage and do t preen each other or even like standing side by side. They're both bobded to me but I've gone through lots of precautions to influence this outcome.
If it were me I would cut the sugar and start having the bird step up onto a stick perch to get the bird out of the cage. Then I would clicker train the bird to come to the cage door or out of the cage and then step up onto hand. Clicker training can really be a game changer for a biting bird.
I hope you and your little one can become even closer. Good luck!