Stop with the free feeding... this is a dog that needs to be on a schedule. And a cup and a half might be too much for a 20lb dog. Try reducing it to a cup. I have also found that feeding 2x's a dog is better than once a day. I have never let my dogs free feed. Once he is on a schedule you can mostly determine when he should have to go... and then you take him out and stay out till he goes. A trick you can use (many don't like this but I will put it out there) is what people that show use. Insert a match in his bum half way.... This will stimulate him to go, when he does praise/treat him. And until he gets the idea, you will need to keep him crated or on leash. You can search the forum for other conversations about using a match to stimulate. Search for match trick