I have a few hard core diggers, and I have found that if you bury carpet, it stops the digging! You would have to do it so far out from the fence so they dont just go under it. Try calling remodelers or salvage places or junk yards or whatever to get used carpet. I swear it works great and grass will grow on top of it fine. I have some out in my yard from at least 6 years ago, and it is still holding strong. It is the only place with no holes lol! Use synthetic carpet with a plastic type backing.
Also for the climbing, what about angling in a width of fence on top of the existing fence? Like prison barbed wire. So they would have to hang almost upside down to climb out.
Good luck!!!!!