Lots of info here!! It is hard isn't it to decide what's right and what's not when it comes to kids food and healthy eating!
I'd say that so long as a child isn't overweight and eating the recommended daily intakes of fruit and veg,and no more that the recommended intake of salt etc...then leave well alone!!
Ensure that he doesn't get a complex regarding his meals. A few basic rules I have in place with my children and charges are that all meals and snacks be at the table...no "eating on the hoof" wandering around the house or in front of the TV. Occasionally as a treat is fine but not the norm.You can eat a lot when watching TV but not if it's on a plate.
Sometimes eating is due to boredom just as some adults comfort eat or boredom snack. Lots of planned activities where eating can't happen...swimming...gym club...story time at the library etc...could fill up your afternoons and not give him the chance to think about eating.
In addition, why not decide to only offer fruit between meals and not anything else? That way, he doesn't keep asking in order to get lots of different choices.
If only to ease your own mind, pop along to your Health visitor with a food diary.
Some parents would give their right arm to have a child that eats as some hardly eat at all. It's all perspective!!
xxKaren