Thank you for taking in this troubled Macaw. Seems to me that he just needs time to settle in and get used to his new surroundings. If it is at all possible to keep him, this would be best for this Macaw. Macaws who get bounced around a lot never seem to make a full recovery. It's true that this Macaw will take time and will need lots of one on one time with you.
The best and fastest way to bond with a Macaw is to adjust your schedule around him. This means when he eats, you eat, if he moves back and forth, you mimic him, make a game of it. If he takes treats as you described give him a few almonds, then take a toilet paper roll, let him see you put the almond or almonds inside, twist the ends and hand it to him, this does two things, first you are interacting with him, you are teaching him to play with a toy and by doing so, he gets a treat.
you can also work with them on stick training, there are many youtube videos to help you on-line.
You can work with the Macaw to step up onto a stick or perch, if he performs this task or any task that you ask of them, reward reward reward. Once he steps up onto you, that's when the real training begins, always take small steps hear as you do not want them to regress backwards. I like to work on the floor on a blanket with my Macaw when i first brought him home, you have better control over the Macaw and some macaws hate the floor and would rather be on your arm. play with them with toys, this way if they are aggressive, let them bite the toy and not you.
Take showers, eat, watch T.V, read to them. All of these actions are bonding time. Keep this thought in the back of your mind, you must allow your macaw to think of you as part of their flock. As time goes by, you will soon learn their body language, when they want you near and sometime, they want to be left alone. Please try to get more info about his past as this really helps understand what they have been through and how to treat them to make their life a bit easier. Thanks for sharing. best of luck Joe
