1 The first thing you need to do is evaluate the Dachshund's body condition. It is easy, see this link,
http://www.puppychow.com/products/po...condition.aspx In most cases, a dog that won't eat is too fat or maybe sick. Sick dogs need to see the vet. Try to figure out a place to put the cat box the cat will continue to use, but the dog can't reach. Same with the cat's food. If she is eating her own poop or the Pug's, try to clean it up before she has a chance. If that doesn't work, add something to their food to stop it, perhaps the cats too. I know both grapefruit juice and canned pumpkin are safe, effective things to add to the dog's food. Might work with the cat too, but I don't know that. There are commercial products too, Deter and Forbid. They might even come with directions on whether you can give it to a cat safely.
Having cut out the poop and cat food, this is how to get her to eat her dog food. Put down the dish with what the dog should eat, and give it 15 minutes to eat. Then take it up. Do not give it anything to eat until its next scheduled meal. In a few days, it should be eating what it needs. Continue to check its ribs and adjust the food as needed. This is not easy. I had a Shepherd go 3 days on a few nibbles. I was a wreck, but she was fine. It is almost unknown for a healthy dog not to eat what it needs. Unfortunately, in too many cases, it is less than the package says, and less than the owner thinks the dog should have. Many dogs are quite good at holding out for tastier chow. Like kids, sometimes it calls for tough love. You might try this on all 3 of them. Put their food out and stand there keeping order until they quit eating. Then take up all the food. Dog food is carefully formulated to be right for dogs, and cat food is right for cats. Both need to be eating their own food.
2 Housebreaking is a common problems. I posted how to do it in a sticky at the top of the dog forum. It is much tougher with an older dog that you must break bad habits.
3 Again, see the sticky on housebreaking.
4 Dogs that do that sometimes have anal gland problems. A vet or maybe a groomer can empty them.
5 4-H dog training is a great idea. You are the right age, and it is the right time of the year. In my area, clubs form soon after the first of the year. Even many urban areas have 4-H. For info look in your phone book under government listings for extension or cooperative extension offices. Ask specifically about a dog or canine club. The dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands a treat. Start at
Raising Your Dog with the Monks of New Skete
Being top dog will make a big difference with the other things including the biting. The 4-H instructor will be able to watch you and your dog and help in ways nobody on the net can. You will have to choose just one dog. That shouldn't be a problem in a good class because it will be about teaching you, not the dog. Just do the same thing with the other dog at home. The instructor may even know more about cats than I do. Some of what I have said about the dogs may or may not work with the cat. You may want to post about the cat to the cat forum.
Having them all spay/neutered will make things much easier and make sure you don't have puppies and kittens to try to find good homes for.
You are not a bad owner. Nobody is born knowing all about dogs and cats. I didn't know that much until my family started raising puppies for a dog guide school when my daughter was about your age. Many very good people helped me, and I can repay them by helping you.
My daughter is now an engineer and takes her puppy to her office.