What age he breeds at or if he even should be bred depends on what you do with him and how he develops as a dog. At 2 years of age when he is fully mature and is seen to be structurally sound then you could do weight pull or some events and put some titles on him and show that he has some reason to be bred.
There are other events you can start younger like Obedience and ABKC or possibly UKC conformation events depending on the dogs structure.
i see im leaning towards weight pulling because he has alot of drive when can i start training him for it without messing with his growth he is 8 months now weighs about 70 pounds could i start him now
You can start training him. Which you can read all about in our weight pull section. However competition require pulling weight that is much to high for the growing body of an dog under 2. Do you have pictures of him? 70Lbs at 8 months sound very large for a pocket bully.