Cats are Stressed Too

One of our cats, Nigel, was peeing and pooping in odd places, for various reasons; like our schedule; he didn't get to go outside. I wanted to put him down because it seemed like the easy way out, but my wife would have none of it. We took him to the vets to see if there was some physical reason for him to do this, but blood tests and a good physical proved otherwise. They told us that the unwanted urination was most likely behavioral due to stress caused by our other three felines. We think part of it is because he was de-clawed by a previous owner.
They like to bully him, he is so afraid of the other ones that he won't use the litter box, and we have three boxes. If there is a piece of clothing laying on the floor, he will go there. More than once he has urinated on our shoes. A couple of times in the past month he has pooped in front of our toilet. That was nice to wake up to at 5 AM. He was also hiding behind a certain love seat in the rec-room for lengthy periods.
The veterinarian suggested that we try a couple of things to ease his stress: One - we tried a diffuser that has some compounds in it that relax cats. It covers about 750 sqft. when it is plugged into an electrical outlet. The other thing we tried was canned cat food, called CD Stress. It contains some drugs that relax cats and give them a sense of well being. It is also very expensive. I give him a can in the morning when I get up and a can in the evening when I go down.
Nigel seems a lot more relaxed now; he doesn't hide all day, he sits in rooms with the other cats and his bad toilet habits have decreased considerably.
This hasn't come cheap. A case of the CD stress is over $50 and lasts 12 days. The diffuser with the first refill is over $50 and a refill is about $35 and will last about a month. Time will tell if this is a permanent solution but Nigel seems a lot happier and this is cause to celebrate.