Hi, have you tried any foraging toys or diy foraging toys? You can use it so he can work for his treats/pellets by getting them out. You could try putting it one of those 7 day pill box cases, make sure it's clear so he can see it. You could also make him search for his treat, for example, hiding some treats in a small open box filled with shredded paper. (Again helps if it's a clear plastic box so he can see that there's a treat in there. It reminds them of their purpose otherwise they might not see the purpose in opening that pill box or digging through that shredded paper.
Those are just a few ideas off the top of my head. I know online they have more good ideas for foraging toys/activities for birds. I bookmarked a few pages on my phone so I can send you some links if you still need them.
Also, if you don't already have one, how about getting him a large parrot playstand (the kind made of real wood, so it's also good for their feet), most ekkies love to climb. In addition, you could also try a hanging a toy or two off of that and see how he reacts to that.
Another thing for the plucking, one website mentioned how they placed a cotton mop head near the bird and now that bird preens and plucks that instead of plucking herself. Of course, you may have to work with him so he's not afraid of it.
