Cat eating issues

Question
My cat won't eat his dry food, but will eat the dog's.  I have tried many brands of dry food and he will only nibble occasionally.  He is also fed wet food which he eats readily.  I want to put him on a diet of half wet and half dry, but he doesn't eat the dry, unless it's dog food.  He will eat the dog food out of the dog's bowl, when his is right near it, and the dog will wait for him to finish before eating.  He is about 4 years old and possibly Maine coon.  I got him off of Craigslist, so don't know any of his history prior.  I had him checked by a vet who says he is perfectly healthy just a tad underweight.  I have had him for about 6 months now, so he is adjusted to the new home.  He does show some signs of having been abused in the past, and am wondering if his eating habits could be due to that.  He won't eat anything at all unless I am in the room with him.  I am concerned that he won't get the necessary nutrition on dog food.  What can I do to ensure that he gets the proper amount of food and nutrition that he needs?

Answer
For this I would actually recommend a couple of things. And I'm sure you are aware of this, but cats are carnivores and definitely require different ingredients than what dogs do, hence why we need to get the cat eating his own food and fast!

The first easy thing to try is put his food into the dog's dish as well as his own. There's a chance that maybe he just likes to eat out of the dog's dish instead...Do this for a couple of feedings and make sure you act like it's the same ritual going on as always. And don't worry about making the dog stay away, you want the situation to seem as normal as possible for your cat.

The next thing to suggest is mixing it as you were, but start with mostly canned a just a few of his own kibble. Then gradually do more kibble and less canned.

Have you tried switching bowls with him to see if maybe he just doesn't like his current dish?

If he's being persistent, go ahead and make a mixture of the dog's food and his own and see what happens.  

Let me know.