Chow has very soft or loose stools

I too have a very picky chow, but I have tried different foods for dogs but he doesn’t seem to like any, he will eat some but then wants none of it again so I worry and try different things but he seems to have potty problem but as we all know not a good thing with all their hair. Our son passed in Oct. and he would help me our dog will turn 3 in July and can be very stubborn. Which I know is their thing. This is our 4th chow but as sweet as he is he has been the most stubborn, I have a MS so can’t chase him and to get him to stand still to cut it out and bathe him is a problem. My question is what is the best thing to give him to eat that could stop the soft stools? He of course wants human food but you never know what will start his stomach problems! I want to cut and trim around there but when I pick up anything to trim it away he leaves lol Help please