hi mad4, had a read of your nutri write-up in Allergies at last.
For us, nutri approach has done more than some drs, inc a consultant or two - but this is with a lot of hindsight now. There is a lot of logic and common sense with nutri approach, but whether nutri or drs, use your gut feeling and go with what you are happy with. What did the nutri say on omeprazole and formula?
It seems to me your ds is locked in a vicious circle of formula and omeprazole and you have to do something to break out of it. If it was me, I would decrease formula intake, either by diluting it (and)/or eliminating evening dose altogether.
I would also steer clear of omeprazole long-term, because prolonged use can be quite damaging. By stopping him from producing digestive enzymes (which is what omep does), his digestion will not normalise and you will be faced with malabsorption and/or prospect of autoimmune conditions, not a good idea.
It could well be that his constipation is due indirectly to omep, which sends signals to his body to further slow down digestion. Also, the standard full quota of ALL ingredients in the formula may not be right for him if his elimination is unable to cope.
However, don't take my word for it, as I am not a dr, but maybe when you are seeing any of your experts, ask their view on long-term use of omep and/or on reducing/discontinuing formula.
As for foods (speaking from experience), you can't beat a home-made soup or caserole; in the meat stock you will have very easy to digest aminoacids, which should be a very gentle introduction to protein. But stay clear from wheat as a thickener, you can use cornflour or ground rice if you have to, but you don't even need that if you use lots of veg.
Did you know that sauerkraut is a natural probiotic? That's because it's fermented naturally. Of course you can't dish up a portion of it to a 11month old, but you can chop up some into a caserole or a soup to add flavour, or just spoon some of the liquid from it into an individual savoury dish.
Hope it gets better for you soon.