LG, I don't have kids at the age of your DS so I don't necessarily have advice about what to do based on my experience as a mother, however, after reading pip2jays' reply, I felt a weird sense of dejavu about what I experienced as a child.

I have worked out that he has a texture aversion.. I know this because his dad does too.. the plate of food has to match his perception of it.. so if food looks dry and then he tastes it and its mushy he gags and cant eat it and vice versa? if there are too many flavours of opposite on the plate he wont touch it.. because he cant tell what flavour he is anticipating.. So for example if its salty and sweet/sour in the same dish. He hates sauces of all and any, even tomato sauce!!! he will eat nuggets now but that took a year of trying.. He mainly eats white foods because they are texturally safe and mostly dry.. I cant even bribe him with "its sweet" no dice.. He is a sepretarian ( our term for it..LOL ) all the flavours must be separated. I had breakthrough this week that he actually had some noodles ( no flavour or topping but again they are white ) while the others had the whole spag bol.. so he prefers completely dry or completely smooth and nothing in between. I am of the firm belief he has a physical problem and its not a power struggle you know..
This sounds a bit like me when I was a child, I remember struggling at meal times and not wanting to eat anything, having a long list of foods I would never eat and being fearful of foods I didn't know. For me the worst was having to deal with mealtimes at other people's houses.... I was especially fearful of foods at other people's houses.

Still, even in familiar territory, my poor mum, whatever she would dish up, I would refuse. It didn't matter whether she put me to bed hungry, I still wouldn't eat. I just couldn't handle eating certain foods. In the end, I think my diet consisted of white rice with soy sauce, plain pasta with butter and white bread with butter. (I shudder to think!!) I must say, this did not ever relate to an eating disorder, it was just 'fussiness' as a child. Mind you, I did eat more than plain rice, bread and pasta, that was always my fallback.

It is only in hindsight now that I realised that I had a real problem with different textures and tastes on my plate. If food tasted differently to how I expected it I would freak out, if foods had textures which didn't "match" I freaked out and I just didn't eat. Pip2jays post described how I felt really well, I only wish that I had a parent who understood as I think it would have made a difference to my fear.

I eventually began to become adventurous with food when I hit my late teens. I just began to enjoy more food then. Now, I will eat anything, love to cook and love different textures and tastes in food - go figure!

Texture aversion is a great description for what I went through. It is interesting to remember that some of us do have hypersensitivity to certain things, some people have a heightened sense of hearing and can pick a pitch problem in a singer that others will never notice, some have a heightened sense of smell and can be put off by the garlic someone had for dinner the night before when others have no idea what the issue is. Maybe your DS has a heightened sense of taste and his poor little brain just cannot compute all of the overwhelming sensation coming at him at meal time.

I say, keep going as you are, take it easy as you go and try the simple, white foods approach. Definitely keep making food fun and not a big deal. Keep leading by example and offering choices.

Then, based on how I felt as a child, maybe try offering your DS food in lots of separate bowls, (similar to a Japanese bento box style) so that food is separated into different tastes and textures. Otherwise, what worked for me was flavorings like soy or butter. Once I was comfortable with these, I would happily douse all foods in soy or butter to mask their flavors otherwise. Using a 'safe' sauce or something similar may be a way for your DS to comfortably try different foods.

I hope something works soon for both you and your DS.