It is well-known that some highly processed commercial dog foods contain lots of additives & colourings that may contribute to hyperactivity, which is why I only feed a complete that is free from artificial additives. Also some foods are too high in protein content & this too can cause increased hyperactivity. It would certainly be worth trying a diet that does not contain colourings & see if there is any difference - if you were happy with the diet Bailey was on when you had him, then it makes sense to go back to it. Having said that, temperament is largely influenced by genetics & rearing/training so you may not notice a huge difference. Often (but not always) puppies that are sold at 6 weeks age tend to be more "nippy" as they do not learn bite inhibition with their littermates & some puppies are just generally more exciteable than others anyway. I think you must just persevere with the training & the instant Bailey starts to get OTT, then put him in another room on his own for a few minutes - you must keep repeating this over & over again until it sinks in that his behaviour leads to him being removed from your company. Also don't play any kind of "rough" games with him, so no pulling on tug toys with him for example.