Update ...
He is out of the cage 4-8 hours per day and gets alot of attention, I gave him the best food I can.
And as I have expected, nothing changed. He has like +10% more feathers on his back, but he still plucks them. Still no colored feathers on the belly.
Now when he got used to being out so long, he screams extremely when he is in his cage.
He never stops, I have tried to ignore him but 3h+ of nonstop screaming was enough for a test...
Now he is out 8+ hours per day. Only after dark, he is quiet and sleeping.
As I see it, there is only one option left.
There would be two, in case I have homeoffice for several next years , but at this stage the only possible solution will be getting another parrot to make him company.
Though this can go so wrong in so many ways, senegals are teritorial and attachable to persons.
Not talking about what to do if they hate each other.
Can you see any other option ?