Even though the vet said those were just feathers, are you sure? They look more like the result of the ungodly union between a maggot and an eggshell.
Anyways, I'd completely detox his system. You'll want to look into Lily of the Desert Liver Detox (you'll probably have to order it online), Bragg's apple cider vinegar, and dandelion root. The Lily of the Desert stuff will detox his whole body pretty much. The ACV you'd add to the water (I forget how much) to kill any yeast he might have in his gut, and it'll help his gut flora establish itself in better ratios, or whatever. The dandelion root is to help get rid of his cancer (look up "dandelion root Windsor" in google).
Put him on a sprout-based diet and mix a generous amount of powdered dandelion root into it. You can get dandelion root from a health food store, then grind it into a powder with a clean coffee grinder.
Make sure to include a good amount of fresh veggies and absolutely no processed foods in his diet. If he enjoys his carbs, you could try making this recipe for birdie bread for him:
Flaxseed (grind it up yourself)
Oats (I think I ground up 2 cups of the stuff to make into flour)
Cooked or sprouted quinoa
Have the ingredients in whatever ratio you want. Oh, and remember to cook it in a glass dish you'd cook dessert squares in, and line the thing with parchment paper. Whenever I cook for my dogs and budgies, I just put whatever I want in whatever ratios I feel like. Obviously I only include safe, healthy ingredients and I make the foods according to their dietary and nutritional requirements. I don't usually bother with recipes, but instead I just let my knowledge guide me.
Oh, and you might want to get some platform perches for him to help him out since his leg is paralyzed. Some rope perches might be nice, and you might want to pad his wooden perches with veterinary wrap to help prevent pressure sores and whatnot.
Oh, and sorry for how informal my post seems. My brain's kind of foggy right now, so the words are broken... Sorry :3.
Oh, my boy, Ju, has had testicular cancer since last October and I've been treating him with dandelion root. He's gotten better and is much happier and outgoing than before I started him on the dandelion root. He still has the cancer, but it hasn't gotten any worse and he's definitely doing better than he was. The dandelion root is completely safe, so you've got nothing to use, giving it to him. You won't see any results for two or three weeks, but then improvements will come on fast
Samantha, Charlie, Ju, Rumi, Lara, Pollo, Ziggy, and Alice
Rest in Peace
Sam, Nova, Joey, Maria, and Scarlet (March 4, 2014)