Booger, I am going to type some stuff for you. If it does not register, or is something you already know, disregard my thoughts. Teaching handling revolves around a logical progression for the dog. Broken down into the most elementary steps, each facet is isolated and taught independently at its simplest level and then expanded. After a strong foundation is built, the facets are slowly linked, one at a time. They are taught first on land. Only after they are solid on land are they brought to the water. The water amplifies any weaknesses in your teaching and tells you what you need to go back to solid ground and clarify with more thorough teaching. When things break down and you can not communicate what you want to the dog, it is most always a weak foundation that lies at the root of the breakdown. A dog tracking your boot tracks is normal and to be expected. A dog not going beyond the decoys is normal if it has not been taught to range beyond them. Range is one of the facets the handler/trainer isolates and establishes through training. From your post, I deduce you are at a loss on how to get past some of your stumbling blocks. Finding a mentor that trains hunt test or field trial retrievers is your best bet to get off high center. The retriever guys are the best at teaching handling. It is their programs we modify and teach our versatile dogs. It is possible to find a trainer who is willing to trade teaching you what you need to understand to help your dog, for helping him in his training, if you are willing to put in some work. The dogs reaction you describe is confusion. Isolating what is breaking down and simplifying is what a mentor will buy you.
Good luck with your dog and don’t give up on it.
Willie