A rough-dry coat, weight loss, bad breath or just an overall poor appearance can be symptoms caused by intestinal worms in dogs. This would be my first concern. .You should be able to observe the worms or the eggs in any fecal matter if he is infected. If you are still uncertain about worms after checking as described above, you can take him to the vet but you can also go to a pharmacy and obtain some medicinal quality sulphur. Mix some of this with some lard or other animal fat, possibly marrow and feed it to him. Probably, for his size, about a half teaspoonful in an ounce or so of the fat. This is a good treatment for dog worms and much cheaper than a visit to the vet. I'd recommend repeating the application in 10 days or so in case unhatched eggs were left in his intestinal tract. The fat is eaten by the worms and the accompanying sulphur will kill them. For best results, deprive your dog of food for 24 hours or so before de-worming. The pork you are feeding him should be discontinued for the time being. Place him on a beef or lamb diet for a while, or a good quality commercial feed that's high in protein. By the way, has he had shots for distemper?
Best of luck!