Hi again Sara!
I have a great book by a nutritionist, Susannah Olivier, called 'what should I feed my baby?' it was recommended to me by a herbalist/naturopath when I had DS1 who had silent reflux. In it she states that the 'nightshade family' of vegetables should be completely avoided as they have compounds to which a young baby may be sensitive. The nightshade family include potatoes, tomatoes, peppers/capsicums and aubergines/eggplant. With Ts sensitive tummy might be worth avoiding these till he is older??? Just a thought, always worked for us :-)
To fill up DS1, who didn't STTN till I started this, I gave him a brown rice purée. I used to mix fruit in to it as a dessert, or mix with veg for dinner. It was like lead in his tummy and filled him up beautifully.
For the constipation issues, a dried apricot purée has always worked wonders here too .... It's so delist I used to sneak it when I was feeding DS1!
HTH, Shell