Chicken and rice almost certainly has helped his stomach; it is nice and bland and easily digestible plus dogs tend to love it. Also the small frequent meals are easier to digest that a large meal all at once. I am glad he sounds like he's doing better. To me it sounds like maybe you are getting some sort of allergic rection to foods as well.

Give him some time on the chicken/rice and maybe now start to work towards fewer, slightly larger meals and see how he does. Then I'd look into a good quality kibble with an alternative protein source, no grains except rice, etc. Laura Lang keeps the Whole Dog Journal list here:

You can also give the chicken/rice meals as an alternative. You can try addding a teaspoon or tablespoon of live yogurt as well weekly or so, but if this bothers him discontinue as perhaps he has sensitivity to dairy products (dogs sometimes do).