As a foster mom to small dogs, I strongly recommend crating. Be sure the crate is small enough so the dog can't poop on one end while sleeping at the other end. It should be just big enough to turn around in and lie down in.
Also, even if you want to change kibble, it's a good idea to feed the dog whatever he's used to until the stressful transition time has passed. I don't know how many times I've had to feed a dog a kibble I hate for a few weeks, until the dog feels comfortable in my home. Stress can do a number on their little tummies.