Ok, first of all birds don't usually get stress bars in just the span of a few weeks. It usually takes that long just to grow a new feather and they don't all come at the same time.
If you want my advice for the healthiest looking plumage (and thus most likely the healthiest overall bird) is don't bother feeding anything else but a high quality pellet. I know you think you're feeding the bird well by giving all this variety, but it in no way ensures that it is getting the nutritional balance it needs.
I've been feeding my two parrots almost exclusively
Roudybush pellets in two very limited meals per day and their plumage is outstanding. I think there are a few other pellet brands that yield similar results to owners but this happens to be the one I go with. The pellet mix you are feeding sounds like junk because everything else mixed in diverts the bird from eating what is actually most healthy. From the way I understand your description of your food management routine, on one hand you are reducing total overeating so the bird is becoming less hormonal, BUT you are feeding a lot of junk food so the bird still isn't getting optimal nutrition.
The best thing you can do for starters is to get a high quality pellet. Transition the bird to it. Free feed it exclusively for about a week or two. Then go to twice a day unlimited feedings of just this pellet. And only after everything is comfortably settled there, we can talk about diluting things using all the other fun foods and setting up motivation.
I don't want to discourage you from seeing the vet (in case there is some underlying health problem hat isn't related to the food) but what it sounds like to me is that it's just an unhealthy diet and that the vet can't do anything besides recommending a pelleted diet (and I know which one they'll recommend because that certain company buys off all the vets). If your bird is still molting (you see a lot of colored feathers falling out regularly), I would really encourage you to make the swap now. If the molt is already over, then there is less urgency but it should still be done. I think it's ok to feed those sorts of foods to the bird in moderation as treats and for fun, but they can't be the basis of the diet. First you must establish a healthy criteria and only then can you venture away from that with all the fun foods, not the other way around.