OTE - spot on!
I also agree about the Pervasive Developmental Disorder (PDD) being the likely problem here, with the connection to Sensory Integration Disorder (SID). Remember, for us in Australia Sensory Integration Disorder (SID) is a sub-set of a number of disorders, notably anything Pervasive Developmental Disorder (PDD). It's just something else we have to deal with.
Interestingly, we've just come home from a picnic for four families of kids on the spectrum (young teens). Some siblings and most parents were also there, we each brought along our own food and pooled it. It was fascinating to watch what everybody chose to eat. Remember, these are kids who have mostly worked through their Sensory Integration Disorder (SID)/dietary issues but not completely. We could also see some of it in other family members. I was very proud of difficult child 3 - he managed to eat two pieces of chocolate cake with creamy icing. Mind you, I did make a point of telling him it wasn't chocolate cream, it was chocolate ganache.
One family brought peanut butter, all their son would eat was peanut butter on a bread roll. He was hungry early and HAD to eat. We tried to feed the kids with us and were mostly successful, although difficult child 3 was late, he was helping a family make sand balls - no common language! He finally washed up and came to the table, ate mostly bread with his favourite salad things. We had an extremely varied spread but it was mostly the adults who shared, the kids zeroed in on their own familiar foods. They happily borrowed cups, plates and knives but food - it had to be familiar. Sensory Integration Disorder (SID) is a huge issue for these kids.
I remember as a child (I suspect there are some Aspie traits in me as well) being a fussy eater. back then there was less variety. I hated foods mixed in together and my mother would always try to encourage me to eat by cutting a piece of meat and pushing potato and peas onto it. Syhe would cook fish and try to entice me to eat by squeezing lemon on it. I was away at a school excursion and we were fed fish - I tried it without lemon (it was that or starve) and discovered I really enjoyed it.
The point is, because I know how it felt not being able to have choice with foods I really was AFRAID of, I've always tried to give my kids choice. Then when I got 'faddy' kids (because of the Sensory Integration Disorder (SID), especially in the boys) I was very glad of modern conveniences and wider choices in foods to be able to help them. Where my mother would boil carrots (which I hated) to feed ten people, I serve some carrots boiled, some raw. The kids all prefer them raw. It's a texture thing. They're still eating carrots.
With Sensory Integration Disorder (SID) kids we often have to break the social and dietary rules of what is considered acceptable. At the same time, when we know they feel calm and relaxed is a good time to encourage them to try something new. Tastes at shopping centre demonstrations are good - the kid knows you couldn't have set it up. You taste too, you and the child are on equal terms with the new experience. And from the sound of it, your son is developing a wider range of possible foods. He does sound like he's covering a lot of food groups, although there are still gaps.
Looking at what he is prepared to accept, it seems to me that he is preferring fairly bland tastes. This could also possibly connect to his food sensitivites (if there are any). Kids with food sensitivies will either crave what they should't have, or avoid it because it makes them feel bad. Stronger flavours are associated with naturally-occurring salicylates, a common allergen.
difficult child 3 was on a special low-allergy diet 18 months ago (it was purgatory). He was frustrated by the lack of variety but when it was explained to him he was supportive, even if annoyed by it. Your son sounds like he is compliant but simply finds a lot of food choices too unacceptable. difficult child 3's diet was extremely limited and definitely not balanced or sufficient. He lost a lot of weight before the dieticians finally accepted that he doesn't have food sensitivity problems causing his symptoms.
Your son likes vanilla (low salicylate). Peanuts are higher in salicylate, cashews are lower. Cashew butter can be made in a blender and is delicious and nutritious. it may be yet another taste to try him with.
Colour seems to matter to him. Also, the yellower biscuits may also have a stronger flavour. The texas toast (thanks for the info, it sounds like what they serve in Sizzler restaurants over here, we've got our own version of the recipe too) could actually be quite nutritious. Will he eat home-made texas toast or does it HAVE to be the packet stuff? If he'll eat the home-made, you might be able to make your own egg- or milk-enriched bread as a base. What sort of cheese is it? Bland like mozzarella, or strong like parmesan?
Have you read "The Curious Incident of the Dog in the Night-Time" by Mark Haddon? It's a novel, told in the first person by a main character who has Asperger's Syndrome and serious food Sensory Integration Disorder (SID) issues. It's a brilliant book, I enjoyed it purely for entertainment, but it's also very enlightening on what it is like from the Aspie's viewpoint. The character in the book doesn't like food to be touching, won't eat brown food (so carries a bottle of red food colouring) and also prefers vanilla (chocolate is brown!) although strawberry (it's red - that's good) is acceptable. He also doesn't like yellow things.
The juice is good - will he try it frozen? It's great especially in summer. What about juice with pureed fruit in it? I know difficult child 3 won't try that, but my other kids will. A vanilla banana smoothie using the supplement? There's a lot of vitamins and nutrition in that if he will eat bananas or drink something with that thick texture.
I agree with the suggestion to check if he has issues with swallowing. A speech pathologist is the person for that and maybe an assessment on language issues as well could be useful.
Have a look at www.childbrain.com
and do their informal online test. You can print the results and take it to his specialists for their opinion.
Will he eat rice? What about risotto? Cooking rice in stock instead of water can increase the protein content and still satisfy his carb craving. It can also be kept fairly bland for him. I cook risotto for my kids but I'm not allowed to put anything extra in it other than the initial bit of onion, and the chicken stock. No pieces of meat, no vegetables, nothing. But it's a great winter meal. They will let me put cheese in it right at the end. Not good if you're trying to LOSE weight, but filling and nourishing. What about pasta? Gnocchi? difficult child 3 loves home-made gnocchi (mashed potato, egg, flour - boiled as thimble-sized dumplings until they float then skimmed out and served with garlic butter) but easy child 2/difficult child 2 hates it (HER issues with Sensory Integration Disorder (SID)!). Home-made pasta & gnocchi are a great way to sneak in extra protein - I make my pasta with whole eggs and flour, no added water.
I dread the day when difficult child 3's favourite brand of frozen fish is no longer available. I've had to trawl the shops sometimes when it's been off the shelves, I stock up when I find it but when I have more in the freezer, he eats it faster.
You're already doing a lot of good stuff.