Aggression in iguanas can be a few things.. He could be driving you out of "his" territory... breeding season (which is one reason I personally would not allow an iguana to free roam my house). Then there is the case of a sick iguana trying to ward you off - Its natural instinct for many animals to force aggression to not look weak when ill, iguanas are no exception.
Realistically your idea of a caged iguana to look at is fine, iguanas are not social animals, they do not prefer for the company of their own kind let alone humans. If you had him in a cage now or a room of his own I would suggest reducing light cycles.. In extreme cases some people do an outright black out for 1-2 weeks to trick their bodies out of mating season.