There is a dog that comes to my work that doesn't limp, but her hips crack so bad that it seems like we are breaking something when she just sits. She doesn't seem painful and doesn't have any issues walking. We have even x-rayed her hips, and found nothing wrong. So my first impression would be to not worry, but how long have you been hearing his joints crack?
And less poo is a normal thing when switching to a better food....is this food a grain free food? If so, whiteish poos are normal with the higher protein level...?