I don't get this kid

I've really been struggling with getting my boy everything he needs nutritionally. He has limitations because of his anal stenosis - no bananas, no apple sauce, no white bread, no white rice - but on top of that, he is becoming increasingly picky. I don't understand. I feel like we're going in the wrong direction. Early on, he wanted anything we were eating. And not just to try it. He would eat substantial amounts of food off of my plate. Complex, highly seasoned foods. Salads. Steamed veg. Anything. But suddenly, all of that went out the window. I have to try over and over to find something he will eat. If it could be considered a bread product, he will eat it. So I try to bake a lot of good things - dried fruits and shredded veggies and seeds and nuts - into muffins and unsweetened cookies. But I know he can't live a life on bread products alone, as much as I may doctor them. So I try. Every time, I try. I try oranges and apples and pears and slices of cheese and grapes and soup and eggs and ..... sigh. I've tried it all. Sometimes I'll succeed, for a bite or two, but then he refuses to eat again.
So, when he reached for a couple of tangerines the other day, you can understand that I assumed he just wanted to play with them. They do look like balls, after all. Since we had so many of them, and he was being a pill, I decided to hand them to him. I watched him roll them and toss them for a minute or two before heading off to do the dishes. Imagine my surprise when I found him like this:

Yep. Eating the sad, beaten up tangerines. Peel and all. What? The last five times I had offered them to him - peeled and segmented, of course - every single segment had ended up on the floor. But look at him tear into this thing:


I watched this strange but fascinating phenomenon for a couple of minutes but then Drake gagged on a large chunk of peel he had torn off and I got nervous. Thinking he would appreciate the gesture, I peeled the rest off for him and handed him back the half eaten tangerine. He lost it. Absolutely lost it. He was so mad at me and refused to have anything further to do with his tangerine.
I'm so confused...

What challenges do you have feeding your family? Any tips or advice? I'd love to hear from you.