Also, he should be in the main hub of your home (excluding the kitchen), so as you are doing things, talk about what you are doing (not in his face), but if you are sweeping the floor, say, "sweeping the floor", or "taking out the trash" or " watching TV" or whatever it is that you are doing or about to do. You can say it from where you are--- don't run over and tell him, but just sort of talk to yourself almost about what you are doing.
1. This will help get him used to your voice.
2. It will expose him to new words.
3. He will start to associate certain words with activities, and that can help them feel less stressed in the long run if they can anticipate routines etc.
Try not to get discouraged because it can take a long time, but if you are patient, it will pay off.
Is he allowed to come out of his cage on his own? That is something that can be a good stepping stone for bonding...if he can do it safely (but he has to be the one who chooses to go back in, come out etc). IF HE CAN BE OUT WITHOUT GOING CRAZY, you basically just open the door and let him chill (he can come out or stay in). If he comes back and goes back in, don't shut him in on that first time, or he will think "if I get out, I need to stay out, or I get locked up the second I return". Let him make the choice, assuming it can be done safely...after he goes back in a few times, you can lock the door, but like I said, you want to make sure he doesn't associate going in with getting locked up.
IF YOU DO THIS THOUGH, you HAVE to be safe about it and you have to make sure you have the time to wait it out because chasing him, toweling him etc should not be part of the plan...If you think he will freak out and slam into walls etc...wait on this...but if he has been out and perched fine etc, he might do okay..I know you said the breeder grabbed him and then he would hang out, right?
That makes me think you could possibly try it safely, but again, he may be super freaked out (I am not sure)
You can block off parts of the room if you need to using tension rods etc, but I would do it ahead of time or that alone could scare the bird...if you can avoid major changes to the room, while keeping it safe, I would do that.
DO make sure windows aren't open and close blinds on large glass ones (ceiling fans off..etc).
Consider covering mirrors and blocking off any ledges that he might try to hide on...
Make sure everyone knows what you are doing so someone doesn't tromp in and open the door (either scaring, squashing or letting him out my mistake).
Do not leave him unattended, but kind of park yourself away from him so that you can see what he is doing, but not so close that you will startle him and cause him to fly etc.
Again-- don't commit to this unless you are willing to spend the day on it. Also, if he doesn't go back in a few hours, you will have to make sure he has food and water, as they can get hypoglycemic easily if they don't eat and drink often.
You don't want to put yourself in the situation where you have to force him into anything..and you don't want to stress him out further by having to catch him etc (normally, a bird will go back to eat etc if they know their cage is a safe-space, but it isn't always a sure bet that it will happen right away, so there is some risk/stress for YOU, if you are committed to doing this safely but also, without force.
It kind of all depends on how comfortable you think he is at your house....hard to say without being there.