Please, Please don't get him declawed. There is nothing worse one can do to a cat.
To keep him from clawing at the furniture keep PLENTY of scratching posts around. We have one cat and she has 5 posts scattered around the house. Also keep a squirt bottle handy for times when they "forget" where their post is.
Having him neutered will help settle him down some.
Declawing means they will take his claws out all the way to their first knuckle it's painful for them. It's inhumane. And he won't be able to defend himself if he happens to get outside. Without his front claws he will not be able to climb a tree if a dog is after him.
You might as well have him put down if your going to take away his only defense. By removing his claws.