13 year old son is a restricted eater

Hello. My 13 year old son has always been a very restricted eater (from early toddlerhood) and I want to work on my thoughts around this.

Background: Son was picky from toddlerhood, had low grade asthma too those early years. It turns out, as we later found out, that he has a disease called Eosinophilic Oesophagitis that impacts his oesophagus & causes inflammation & swallowing difficulties. Thus he’s had numerous investigations and treatments for that over the years (at least 4 times endoscopies with general anaesthesia), was on an elimination diet and currently remains on a dairy free diet.

He’s a lovely 13 year old in every way, an ordinary happy boy, however his eating remains (apart from the dairy free aspect) very very limited & unimaginative. He is also very sensitive to smells & tastes and I almost think he has a phobia / aversion (???) to new tastes. Our approach has always been to give him space & just encourage tasting, but not pushing. But his diet has remained largely the same. I struggle with this and haven’t ever made peace with it, but try to keep my feelings to myself to respect his independence.

Here’s my model on it. I would love some feedback and may come back to this.

Model on Unintentional Thought:
C: 13 year old son’s eating habits
T: I’m not a good mother. His eating is so restricted still. I’ve done nothing to help him.
F: guilt
A: stuck in inaction – avoid thinking about his eating habits (thinking there’s nothing I can do)
tend to forget even the basics – his eating is already restricted but I offer him the same things over, have given up
thinking – he’s 13, I can’t control his eating
beating myself up about ‘what good mothers do with their children’s eating’
worrying about his social life & future life
worrying about his enjoyment of food: will that be something he just doesn’t experience in life?
self-attacking thoughts
R: result is his eating remains restricted