If he will eat Ziwipeak, I'd definitely recommend it. I've been trying to feed it to Gemma for about a week now and she just spits it out, lol. Even when I process it in a blender so it's just crumbs and mix it in with canned ZP (which she loves), she just licks off the moisture and spits out the dry crumbs. She's a brat. 
But anyways, any premade raw is going to be better than Orijen. It will probably help with his smelly, soft poop as well. You can probably just let him eat as much as he wants since he's really still so young. He'll eat what he needs to. He may look chubby right now because he's still young and has that fat puppy build, which is perfectly normal and signals he is healthy. Puppies usually don't start to mature into their slender adult shapes until around 4 or 5 months.
I know that Orijen is very high in protein, so it may not work out with him. A lot of dogs just don't do well on it because of the very high protein content.
But anyways, any premade raw is going to be better than Orijen. It will probably help with his smelly, soft poop as well. You can probably just let him eat as much as he wants since he's really still so young. He'll eat what he needs to. He may look chubby right now because he's still young and has that fat puppy build, which is perfectly normal and signals he is healthy. Puppies usually don't start to mature into their slender adult shapes until around 4 or 5 months.
I know that Orijen is very high in protein, so it may not work out with him. A lot of dogs just don't do well on it because of the very high protein content.