Tortoiseshell, it does look like your DS is eating a very good, balanced diet. With my sister (now 25!!), I can entirely understand it.
About a year ago, she went to the GP to say she wanted to do something about her restricted diet. She listed everything she ate-
So, baked beans, peas, boiled potatoes, carrots, mince, chicken breast, milk, apple/orange juice with no bits in, chocolate, Heinz tomato soup, and maybe a fishfinger or two.
The GP said to her -oh, you don't need to see a specialist (Ie, psychologist, or nutritionist, or therapist.... to get to the root of this problem she's had all her life), your diet is fine, you get everything you need, go away and stop worrying.
This reaction from the GP pissed me off beyond belief. It has taken her this long to pluck up the courage and say to a professional 'I have a problem, and I want to sort it out somehow', and to have th GP dismiss her so off-hand. Ggggrrr...
The problem is not nutritional, it's social! She HATES going out for dinner with people, over to people's houses, HATES having to explain herself, gets embarrassed, HATES to have attention brought to the fact that she has these hangups.....
Sorting out food phobias and fussiness is not necessarily always to do with the nutritional impact. It's got everything to do with how this child is going to cope as an adult in later life and just get on with it.
I think you are doing exactly all the right things Tortoiseshell. If you can hide stuff, do. There will get to a point you can rationalise with your son, say he's eaten X before, then slowly show him you putting it in the food..... then slowly stop blending it (with my sister, she won't eat onion, so I started blending it, and putting it in bolognese etc... if she was staying with us... told her later, now she knows it's there she'll still eat it. Next step, NO BLENDING!!! Then maybe after that tinned 'limpy' tomato and not passata..!!)
It may take years, but slow and steady wins the race right? Your DS is lucky to have such a dedicated, intelligent, inventive(!) mother who puts the time and energy into it. I think the girl in the news' parents just don't / haven't put the time and energy into it. Well, not enough anyway. And certainly not soon enough!!