The universal feeding rule with your kind of iguana is to heap their plates high, and if they finish it, give another heap, and another, and so on. You could say, by nature iguanas can't overeat and must eat until they voluntarily stop. BUT.
But many things. If he is dehydrated and eats anyway, his body will rob itself of metabolic water to do digestion with and that will damage his kidneys, etc. Dehydration is deadly. Enough water every day is very important. Feed his leafy greens and veggies sopping wet.
It's wonderful that he's eating greens on his own. He's designed to eat a low nutrient high volume foliage exclusive diet. He's an obligate folivore. The egg was a bad idea. Animal protein will at some point damage his kidneys.
Down in his gut, colonies of good bacteria digest the stems and leftovers (Oh well), like cows digest their grass, providing carbohydrates. Moving back and forth between the cool and warm ends controls how active the organisms are. The iguana's body tells him exactly what to do. Without the heat differential, he can't digest.
Do you know he needs special lighting called UVB? Do you know he needs specific temperatures, one temperature at the warm side at about 90-95F and 75-80F at the cool side. The cage needs to be large enough to have two sets of temperatures. A goldfish tank will kill him. It all makes sense, but only when you know almost all of his needs.
There is much more that he critically needs right now. This is one of the best sets of articles on iguana care. Your iguana needs you to read all of it right away: