Kimberley,
So thankful that Rebel was found!!!! Could Rebel be injured somehow that doesn't readily show? Dogs who are hurting can be very grumpy. You may want to get the vet to check him out. He may also have some thoughts on other possible causes for the personality change.
As far as the fence. My suggestion would be to dig a trench at the base of the fence and pour a concrete curb that is 1/2" or so below the boards. You could even do it yourself with Sack-crete (not sure that is spelled correctly), but it contains all the ingredients, you just add water.
Our dog run is Yorkie proof. We have a concrete curb with a steel tubing fence with the tubing spaced close enough that even Zoe can't get out. This is because of escape problems we had with the traditional board fences we have here in our "hick" town. The steel fencing is expensive for a whole yard, but the concrete curb with your exising board fence should do the trick.
