The hiss could be viewed either defensive or aggressive I guess I would have to view it first - if your iguana is trying to avoid contact, tail whip and then going for a bite this is completely defensive behavior. The dewlap flaring up is his way of saying "I'm a big dude leave me alone."
The only way to do get out of this is not to back off from this behavior (or he learns to do this).. And to take him out of his cage multiple times daily. It can take a week, a month sometimes even longer but you have to take him to neutral ground.. Even the doggy dog tamest of iguanas are known to be defensive in their cages as thats their turf - Iguanas are known to be territorial creatures by habit so basically its useless to try to socialize with them within those boundries. Of course offering them a banana certainly helps set the mood if you happen to swing by the cage with one.. They go completely nuts for them.
I will often times suggest to people to take their iguana to a room that is small and can be closed off from the rest of the house. Preferably without breakables. Just place him in there with you, let him explore etc. Eventually he's going to get curious and walk around you. Now if you happen to set him down in your own house and he happens to charge at you.. You've got yourself an aggressive little bastard so be careful.
Oh and about his tail.. Toss hand towel on him in the cage when you get him out.. It will stop him dead in his tracks. And when he's in your hands hold him firmly to your body to prevent his tail from getting swinging strength. This will minimize the damage to both of you.