Hello! First time typing here, I'm not a native English speaker so please be understanding of any typos!
I own a African Grey parrot, male, 4 years old, had him since a small hatchling, spend time around people being spoiled and all, and overall really cuddly and nice! But also after a year we had this big party in the house and of course, I kept him away from the crowd of people (he was in different part of the house in closed room) but, people being people let themselves in the room where he was, despite me telling them not to do that because he's sleeping, constantly grabbing him and passing around like a toy (they were just amazed of seeing a parrot). Needless to say that petrified my parrot which caused it also to bite me that night for the first time ever, and sadly since then to even now there would be these waves of aggression.
Things he would do is fly to me or others and bite their ears, bite fingers when the opportunity, or just sneak up to you to bite really hard, especially if you get up and turn your back at him he'll seek the opportunity to fly at your neck to bite.
It's been 3 years since the incident and I still regret that I didnt kept a better eye as I should because he is refusing to even get out of the cage now,and I feel it might be my fault because I couldnt really figure it out what was the reason for sudden aggression for months, so there would just be half a day of him being sweet and other half just being angry at me. When hes in cage hes very talkative and lets me pet him and demands scratches and love and hugs but also for some reason tends to use that just to attack me and others in the house. He tends to let me snuggle with him to this day but also the same doesnt matter flying into my face to fight. We used to do the stepping up training but stopped because there wasnt any good time for him to be willing to do it...So we just stopped with any type of training because he seemed more suspicious of my intention whenever I said 'step up'.
I just wonder is there any type of training I can do? He had great first year and all just got smashed in one night and I just want to help him be the little explorer guy he was, now he just refuses to leave his cage. I love him to death but the day is spend him not doing much but just talking and singing from his cage because before he would go around the place, flying and walking and just being interested in toys. I work from home as a freelancer so I have all day for him.
I'm very desperate so any help is appreciated, thank you for reading!