Dog Food Calculator
At 5 pounds and a typical activity level, an adult yorkie needs 204 or ~200 calories a day. If you have a puppy, they could require as much as 2x that amount if they are a younger puppy or only slightly more if they are closer to full grown. I believe that most 1 oz Primal nuggets are 40 to 65 calories each depending on which variety you choose. So if you give just 1/2 a nugget, that's only 20-33 calories. I'd probably feed close to the lower end of whatever Orijen recommends for that specific weight and go from there based on how much the weight changes! What formulas are you interested in trying?
Also I was looking into Orijen/Acana for Toki! How does your pup do on the Orijen? I'm concerned it may be too rich for Toki but I might just have to feed a smaller amount.