Hi Krieng,
Beautiful baby, your wife made a perfect choice with Sunny.
I was going to add that by the looks of your birds tail feather length he appears to be closer to 3-4 months old. In fact, my baby macaw is 12 weeks old and has about the same tail growth. In that case, I would be feeding him up to 90cc per feeding (3 times a day) if he will take that much. Slowly, I would cut down the mid-day feeding amount if he eats on his own during the day, but continue to feed the most at night. I would also start giving him vegetables (corn, peas, beans) and nuts. When buying nuts, buy them in the shell and crack them a bit for him, then he can play with the nut and learn to get the meat out. As long as your bird does not throw up the hand-feeding food and he is willingly bobbing for it, you will not be over-feeding him. Also don't let him have the apple seeds when you give him apple. The more energy he gains from being hand-fed the more he will want to eat on his own 100%, so your right, keep hand feeding till he refuses.
I would buy your harness now and start placing it on him every time you go outside, the Aviator harness is amazing!
Enjoy your baby!