Hi dawn! Good to see you posting
I know it has been a busy year for you! I hope the food is going over well- what came to my mind that is budget friendly, has chicken and rice options and is digestive friendly is the Nutri source brand. They do a really good job with their pre and pro biotics and a lot of folks that I have worked with who have Tummy sensitive dogs have done very well on their brand. A bag of their regular line foods is approx 45$ for thirty pounds (As opposed to 63$ for 24 lbs). I know they have some weight reduction foods but I haven't looked into that brand for small breed bites. If you are still needing digestive support after the switch this may be one to look at.
Lilah has actually done really well on royal canin and they have a pretty amazing amount of research that they participate in as a brand, their long standing reputation has a little more to it than is sometimes recognized. For my girl after some long term eating struggles it was really a godsend. We have not historically done well on grain free diets but we are currently having success with natural balance duck and potato.
Good luck with your dog food search!