Timberwolf Lamb and Apple

I was thinking about trying Timbewolf Organics Nutrient Dense Lamb and Apple formula.  The woman at the pet supply store said it was very high in fat, however, I have a terrier who's pretty active, but not a working dog. I like to give him variety and he does well on anything, but chicken (constipation).  I want to give this a shot, but I want your opinion (ingredients below).
 
Also on the Timberwolf website I found a general feeding instructions for all the food, but I believe this particular Lamb and Apple formula is nutrient dense.  Infact Timberwolf even call's it nutrient dense.  Should I still feed 3/4 a cup a day for a 20lb dog?  I also feed raw, so I will feed less than what is recommended anyways.
 
One last question.  I've fed Timberwolf Elk and Bison before and for some reason his teeth became very brown after feeding these formulas.  Joey has a very noticable underbite, so I brush his teeth weekly, but with these forumlas his teeth were brown before the end of the week.
 
Lamb, Salmon Meal, Lamb Meal, Salmon, Whole Ground Oats, Whole Ground Barley, Whole Ground Brown Rice, Chicken Fat (preserved with mixed tocopherols and rosemary extract), Whole Ground Flaxseed, Unrefined Walnut Oil, Watercress, Spinach, Celery, Parsley, Fennel Seed, Dried Goat#%92s Milk, Atlantic Kelp, Alfalfa Leaf, Wild Salmon Oil, Cottage Cheese, Potassium Chloride, Rosemary, Apples, Cinnamon, Thyme, Dried Carrots, Anise Seed, Ginger Root, Basil, Dried Mint, Choline Chloride, Lecithin, Probiotics: (Lactobacillus Acidophilus, Lactobacillus Casei, Lactobacillus Lactis, Bacillus Bifidum, Streptococcus Diacetilactis, Bacillus Subtillus), Taurine, Mixed Tocopherols (a source of vitamin E), Lysine, Zinc Proteinate, Iron Proteinate, Manganese Proteinate, Thiamine, Methionine, Carnitine, Niacin, Vitamin A Supplement, Calcium Pantothenate, Riboflavin Supplement, Vitamin B12 Supplement, Iodine Proteinate, Vitamin D3 Supplement, Biotin, Folic Acid, Pyridoxine (a source of vitamin B6), Copper Proteinate, Selenium Proteinate, Cobalt Proteinate, Papain, Yucca Schidigera Extract.
PROTEIN: 28%
FAT: 18%
FIBER: 3%
MOISTURE: 9%
ASH: 6.9%
Kcal/kg: 3,920
OMEGA-6 FATTY ACIDS: 3.8%
OMEGA-3 FATTY ACIDS: 1.3%
CALCIUM: 1.8%
PHOSPHOROUS: 1.4
VITAMIN A: 22,000 IU/KG
VITAMIN D: 1,200 IU/KG
VITAMIN E: 350 IU/KG
COPPER: 16mg/KG