hello and some of us are here to support, not wave smug judgey pants around.
I would suggest that your biggest problem is sugar, especially if he starting to put on weight. Sugar is so addictive for all of us, me included (I hAve just eaten far too much chocolate this evening). Things don't taste right for a while when we cut down on sugar and salt, so I am not surprised your LO finds things tasteless and boring if they are not what he is used to. That doesn't necessarily mean he is a fussy eater in itself - everyone has this reaction.
The problem you have, of course, is that we all find this hard even as adults who care and want to do better. When you are seven, you don't care if food is healthy, you just want what you like.
It might be worth moving away from nearly sweet substitutes to savoury. Scrambled eggs on buttery toast would be much better. Omelettes for breakfast are good too but he may be too young for them. You can microwave frozen blueberries for 1-2 minutes and you get a kind of jam that is great with porridge. Most kids I know don't like slimy porridge, they like the jumbo oats stuff. There's nothing wrong with a slice of ham or cheese for breakfast, that's what they eat further north, say in Sweden. You could make a toasted cheese sandwich. They smell great.
Having experienced feeding a very disabled child who absolutely cannot be reasoned with or bribed, I would say its about creating temptation and anticipation. So something that smells great, like bacon or toast, means you are halfway there.
As for juice, I personally think sweet fluids are not your friend in this situation. They fill them up and feed the sugar habit. I gave weak tea at this age- actually mainly milk, but served with a big helping of "ooh you are nearly old enough for grown up tea, oh go on then, as a treat". Some ppl say tea is bad for them, but its better than squash or fruit juice.