Ok too many questions lumped in one set of sentences.
First of I have no problem getting almost 100% faders in my rt project first gen by the time they are 3-4 inches. I will let a secret out , it all depends on the stock you begin with. You can believe or disbelieve me as it does not matter to me but it is the truth. To many that try and make a cross with a set goal in mind just pick two fish and put them together without knowing the genetics behind the fish being paired. So when it comes to the fading gene I will tell you only one half of the gene is needed to express itself but not every fish carrying half a dose will express it. The other problem is (and this is and has been proven on this forum) no given time frame for the fading process to happen so it can be years before a fish fades. Now if the fader fish used in ones breeding only carries half a dose then yes at best only 50% of the offspring could fade or carry the gene. So if two fish that carried half a dose each were paired together 25% could carry a full set of the gene 50% could carry a half dose some expressing it and the rest not and 25% could carry nothing of the gene. Going on this one can see it is easy to get results the first generation from known/proven stock but from then on it gets more complicated.
Second how does one get back to 100% fading gene? By breeding your fading offspring back to a fish with a known full set of the gene. Doing so will give you 50% full set of the gene 25% with a half dose but expressing it and 25% having a half dose but not expressing it yet. Important part is 100% will carry at least half a dose. Now while not perfect if you keep only the ones that fade very early there is a good chance these will be mostly the ones with a full set of the gene. From here you can go to ways, one go back yet again to the fader parent or try and find fertile sib pairs to breed. If you choose breed back to the parent again take the best and fastest fading offspring and sib breed them. Now the last step to prove they have a full dose of the gene for fading is breed them to a fish known to not carry the gene with them. If 50% or more of the resulting offspring fade or show fading genetics then the fader fish has a full or 100% dose of the gene. All together you may be looking at 4 to 6 yrs for this project from start to finish. Once done though you would have your very own line of faders that carry the genetics you want for your breeding projects. I am now on my third gen soon to be forth gen of my project line.
Third and again there are parrots that do not or have not faded of very large size out there. I will try and get time to stop in at an asian restaurant in olympia that has or had an 8"+ non faded parrot and get a picture. It has been about a yr since I have eaten there.