I think it is the depression making you feel unecessarily guilty. You feel guilty right now because you think you don't look after your dog well enough. You would feel guilty if you decided not to keep her, it would be a forever decision that you couldn't change.

Lots of dogs eat stuff they are not meant to no matter how well cared for they are, it how vets get rich The last time my dog was ill and she was in the doggy ER, the dog in the next kennel belonged to a vet nurse and it had eaten pan scrubbers

You are doing a great job, play and grooming are very important for a dog's wellbeing. They bond with us and it our attention they want most of all. Sure they love to play with other dogs in the park but they feel a much stronger attachment to their "family". Dogs are very sensitive to our needs, so when she is lying quietly beside you it doesn't mean she is down or low, just that she knows that you need companionship and comfort.

Don't be too hard on yourself, I wouldn't get by without my dog and although she has missed a few walks, she is doing just great. I've never trained her beyond keeping clean in the house, sit and work on her recall. My vet always says she is one of the best behaved dogs she sees.

Taking care of your dog will help you in the long run, just posting about your concerns shows how important she is to you.