For me the most difficult thing was to break all the concepts in my mind about a healthy nutrition for a infant. While all moms are looking for fat free food, I last hours in the supermarket looking high calories.
Other thing to do is to learn to "read" the pooh, and to deal with the enzymes.
about meals, what i forget to tell you before is to put a bit of salt in every meal, and if it is to hoy, you should put more. And always have a juice for him, so he can drink all whta he wants all time.
every week i give diferent things, depends in what is less expensive.
i only avoid sea-food (but i give her salom once a week is very unexpensive where i live), sausage and all sort of coke,etc, but like any other infant.
i really recommend you the legume, try first without the skin, sometimes you can find legume like beens without skin in the market, if not after cooking eat mash it.
and take advantage of the dessert to put a lot of calories: bananas (lot of calories) with condensed milk or honey like dessert, grate with grate coco nut and condensed milk (i am gaining weight as well).
and raisin i always have in a place where she can take all what she wants (each one is 3 calories). I think (but i am not sure) that raisin dosen´t need enzymes, i never give to her enzymes to eat it beacause it is a fruit,but ask a doctor about that.
hope i can help you, but be patient, and your boy is like any other boy but , in this subject, he is lucky he can eat as much as he want.