Poor you. Hope Nacho is feeling better soon. Just wanted to say, when you wean him back onto a food of your choice - one of the better brands hopefully - do it VERY gradually. Ideally over 10 days. I know it sounds extreme but it sounds like his system has had a bit of a rough time of it lately. I would keep him on the chicken and rice for a week then start mixing in a little kibble, gradually increasing over the following 10 days whilst reducing the amount of chicken and rice.
For treats I make tuna bread as follows:
Tin of tuna (in oil or water, not brine)
A little oil (if tuna not in oil)
1 egg
Garlic powder
Plain flour (or rice/potato flour in case of wheat sensitivity)
Drain tuna (if it is in water, otherwise just put tuna and oil in a bowl)
Add a tbs of oil (if necessary) if you want to, some prefer to mix with water
Add the egg
Add some garlic powder
Add flour - enough to make a stiff dough but not too dry or it is really crumbly
Mix it all up and spread it on a dinner plate about 1cm thick. Put another plate over it and cook in mocrowave for 3 mins.
Cut into small squares when it is cool, store in the fridge for 4-5 days (although ours is always gone in about 2-3 days with training and treat ball usage!)