14.5" from the top of his head to tip of his tail is about the best rough measurement we've been able to get. He's not too interested in letting us use a measuring tape on him and squirms a lot to avoid it
2 days ago I started then putting him on the floor where he will readily step up on my hand!!!
This tells me he KNOWS how to step up to a hand and TRUSTS that you won't hurt him while he's on your hand. He just CHOOSES to be stubborn when he is not in a situation where he's uncomfortable. Many amazons don't particularly like being on the floor (they are prey animals and stay up high in the trees in nature) so they'll bring out the charm for you to save their butt from being 'venerable' and 'exposed' down there:20:. When he's up on his cage, or the couch or wherever he doesn't feel so venerable and in need of help from a human, he can then be more choosy about his preferred mode of transportation and do the whole lunging and refusing to follow the step up command bit.
He doesn't sound like a "scared and tortured soul" who needs very gentle trust building, he more like a stubborn bird with a slight attitude problem who needs his ego knocked down a notch. Obviously, you don't want to be mean, but you do need to build trust while still teaching him how he needs to behave in your "flock". I personally suggest step up drills, away from his cage and comfort zone. If he's confident with a stick, start with that. Have him step down and then back up from many different places in the house (the back of chairs, the kitchen counter, the shower curtain rod, the bed, the floor ext..). This also builds a good kind of confidence and familiarizes him with his new home

Be sure he is given verbal praise and a treat each time he steps up to the stick. Once he is more comfortable and confident in his new environment, then start easing him into stepping to you hand.
We used the old fashion, shameless luring technique to entice Kiwi to get on our hands:54: And he had never been handled before, so you'll have a much easier time getting Gus to try it (who already knows this drill:20

. Basically, you start by placing your hand in front of the bird while offering a treat in the other hand. The treat hand should be positioned behind the "step up" hand just far enough back he has to reach over your step up hand to get the treat. When you first present the treat give the verbal "step up" command to cue him in to listen for it. When he reaches over your hand to get the treat, verbally praise him (good bird!). Once he is proficient at reaching over your hand, move the treat back so he must actually climb onto your hand to retrieve it. Again, cue him to "step up" as soon as you present the treat, and when he steps on your hand, verbally praise him. More than likely, he'll grab he treat and run back to his cage to eat it. You should allow him to do this until he has no hesitation about climbing on your hand. Once he does though, it's time to let him get on your hand and move it about 2' back from the cage before giving him the treat and allow him to eat it on your hand before setting him back down. From there, start step up drills again from all different place, only using your hand instead of a stick

You can also drop the treat every time and just verbally praise (and if he likes any kind of affection, thats a good reward too, Kiwi likes giving kisses so we reward him with those). Also, don't neglect to use the stick once he steps to your hand. Use BOTH regularly. You'll appreciate him being stick trained when breeding season comes and he is in a most foul mood (and you want some distance between him and your flesh lol).