It could kill him by accident, as we are new to this after all, and who knows what could happen if we die while in a human's body?
Nope, im not in his body physically, just the same as you aren't in the body of a fish or a fox that you are controllling. It's just brain manipulation, if it was full possession then the body would be godlike (eg. faster and stronger). If controlling him killed him by accident, then he would already be dead last season.
It should require a large amount of energy. Let's think about it. Possessing an intelligent creature for long enough to teach everyone in the tribe about skinning animals -WITHOUT DAGGERS- and teaching them that if they leave it in the sun, it makes leather.
sure its complex, but no more then making a fire that burns eternally with no fuel, or creating something out of nothing, or even more difficult then permanently changing something's behavior.
if nonan had the option of being creative with a small chance of failure, or being boring and unoriginal with none, then he would chose the boring option 9/10 times, since greater efficency means more profit and since he is the god of money, he will chose more profit. So i just trying to do what my god would do.
A key economic principle is risk/reward. Generally, the more the risk, the greater the reward.
To some extent yes, but if you can chose to do something two ways, the riskier way, or the safe way, and both have the same result, and cost about as much time/energy/money, then a smart person will chose the safer way. In this case, sure, doing it another way might have cost a bit less energy (a dream), but it would have a much higher change of failing, since i want him to something pretty complex.