Try tapping his nose--very lightly--as you say "No" in a stern, but not yelling, voice when he starts biting. Then cross your arms in front of you (so he can't nip at your hands) and turn your back on him for just a moment. Then give him a toy to chew on. Offer him a suitable chew toy as soon as you say No Biting, so he'll learn what is okay to chew on--a toy--and what isn't okay to chew on--you! At 4 months he's still getting his baby teeth. Once he stops teething his chewing should get better.
How does he open the fridge? I agree with the spray bottle idea, again accompanied by a No in a stern voice. Also, try not to give him food directly from the fridge--maybe he thinks everything in the "big white box" is his!!
I'm sorry I can't think of anything about the cat. Does your cat try to get away from him? If not, maybe it's some sort of game for the cat too! When my Shiloh was a puppy she used to latch on to the fur on my standard poodle's legs, and Coco would just continue to walk abound dragging Shiloh with him. I guess it didn't hurt Coco, and he and Shiloh were always the best of friends.
I never took Shi to obedience classes, but wish I had. You might want to ask your vet if he thinks your babe is too young to start obedience training.
Oh, and one last thing:try to take him outside for walks as often as you can. Give him lots of fresh air and exercise, like a baby. (Which he is!) A tired beagle is a good beagle! :biglaugh:
What's your babe's name? Do you have pictures?