Q: How can I stop my three-year-old tabby from biting or scratching me? I have sprayed water at him, pinched his scruff and spent more time with him, but there hasn’t been a change in his behaviour. He’s usually alone in a room when I’m out because I also have a dog who does not like cats.
First of all, is your cat really biting you? Cats bite when they feel threatened and they normally sink their teeth in and will only release when they know they have done some damage. As a breeder, I know when my cats want to bite; their ears point downwards, their eyes narrow, and their tails will be swishing. From your description, it seems like your tabby is play-biting instead.
Here's what you can do, although it may not eliminate the behaviour totally; the goal here is to gradually reduce it. Instead of playing with him using your hands, use his favourite toys instead. Teaser toys such as wand toys would be a good choice. Do it over a few weeks, until he stops trying to attack your hands or legs then gradually start petting him more often. If he starts play-biting again, stop playtime altogether. Repeat this process daily until your tabby stops trying to bite. Remember to reward your pet with a treat each time he allows you to pet him without trying to mouth you.
Lastly, you mentioned that your dog does not like cats. This could cause your tabby to become agitated. To curb this, a proper introduction should be made in order for the two to get to know each other better.
Picture source: http://threesecondsofdeadair.files.wordpress.com