With all those requirements, I would go with an Argentine Black and White Tegu. A new hatchling will fit great in there, but only for about 6 months. These guys love to be held, and weirdly they seem to crave human attention. Super smart, trainable and gentle when handled frequently. Just know that they do grow large and will need an 8 foot enclosure within a couple years. It seems like you have general herper knowledge and could handle something like this. They are truly wonderful pets!