I had a 38 year old blue front who was not just a shoulder bird, but a head in the eye socket bird...
If he's calm and trustworthy, and doesn't bite, and has been trained as a shoulder bird, I wouldn't worry about that so much, and trying to keep him off of there may actually cause more problems than it is worth if he behaves... Almost all of the amazons I have ever had were shoulder birds (despite what the book says.) And most of them CAME TO ME as "biters." Some of them were "maimers." (That would be the bird that now curls up into a ball with her head upside down on my shoulder, and uses my cheek for a pillow!)
Just my two cents.
Amazons are food oriented. Switch him over with some seed mix in with the pellets, and then just gradually reduce the amount of seed. He'll eat.
Vitamin A foods for fresh, especially carrots and sweet potatoes.
He will speak and understand what ever you teach him to speak and understand.
Offering the bird two fingers is pretty universal for step up. I never used voice commands for that one.
Holding a foot in the air is pretty universal for pick me up... same deal.
The rest he will learn over time. And if he's only 5, you have an entire lifetime to teach this bird...
Blue fronts are my absolute favorite Amazon, by the way, and my most bonded bird EVER was my BFA...
They are excitable, but the more you handle them, the more interactive they become.
Just don't let him go into the zon overload on your person, or try to pick him up in zon overload, which is where their bad reputations come from.
Amazon body language means something. LEARN IT!!!