It seems as though your iguana was "calm" before because it was still freaked out from its new surroundings. Iguanas take a lot of time to adjust to their new environment. So in actuality, you ig is most likely displaying his usual temperment which is unfortunately mean and jumpy. Same with the eating problem; your ig just needs time to adjust. My Miles did the same when I got him. As long as he is eating atleast a little bit of his food each day, he should be fine. Try offering fruits mixed up in his food. Starfruit gets my Ig crazy to eat!
Also, when he is jumpy, as you said, try approaching him from the back and with both hands. NEVER GRAB HIM FROM THE TOP. Always scoop up from under his back legs first near his vent and then try approaching the front. Also, a little less orthodox method that works with my IG is by holding the misting bottle in one hand, and while misting, the ig tends to relax, so that would be a perfect time to scoop him up. Also you could try taunting him with a treat form the front, while you scoop him from the back. If all this doesnt work and you ig seems to be even more jumpy and still doesnt eat after about another 2-3 weeks, consult a vet. Good luck.