Ron, First off I am not training expert, but I have had 2 Labs. First I would recommend getting a 50 foot check cord. Cabelas sells orange ones that are easy to see. Buy a couple of retriever bumbers with the throwing knobs attached or get a duck bumper made by Dokken
Dokken Ducks -- Deadfowl Retriever Trainers.
Then get a video or a book by one of the experts such as Hickox or Lardy or the classic Water Dogs by Richard Walters.
Dog Training Books and Magazines.
Read the books, watch the videos and keep the check cord tied to your retrieving machine. The check cord is what makes him bring the bumber to you, not treats. The way you are using the treats, he has taught you to give him treats when he is bad and playing keep-away. Don't use the treats.
Go slow, 10 minutes in a session, a couple of sessions a day if possible. When he gets bored stop. Always finish on a positive. Don't punish him for a lack of retrieve by stoping the session. Make him do something good to finish.
Again I am no expert, but my 1 year old sounded just like yours and she is now quite reliable. If your dog is reliably coming when called, you have a big part of the battle won. You just need her to understand there is no option but coming when called, even with a ball or a bumper in her chops.
Also, you can get professional help for free from a local Labrador Retriever Club. Where are you, I may be able to point you in a direction. The Huron Labrador Retriever club in southern Michigan is open to the public for training 1 Saturday a month. It costs $10.00 and they have everything you need to get started, plus a lot of good advice.
Have patience and do not get mad at your dog, which can be the hardest part of this whole thing.
Once you give your dog a job that you can do every day, he will become a better part of your family.
My Dog Bailey asks to go "play ducks" twice a day and she gets a good work out. Once you get making progress you can make the sessions longer to wear her out more.
Good luck, let me know if you have questions.
Stonecove