ps - another thing only to think about and
please ask questions about it as I've never used it - but there's a product called 'Rescue Remedy' for anxious dogs - I don't advocate giving dogs something like this but heard for many it's worked wonders for other types of behavior ...based on what I've read it has a calming effect
You'd have to take in his age - his behavior and also - advise from those who HAVE used it but it's another thought if you feel he's overly anxious being confined.....
There's posts about it here and on the net (google) but ask your vet first !!
I think it's all natural but again - I've NEVER used it and this would be a last resort ....it possibly could help him get thru the destructive stage.
I'd try to not rely on something like that but it depends on how bad things are and worth looking into if you feel nothing else will work.
I stress though - ask your vet first ! It's scary giving them something that may have adverse effects but like I said - sometimes we need a little help if something is out of control and you feel he may be a danger to himself if he keeps chewing on things he shouldn't be....
I guess I was lucky with my girls - I never had that kind of thing happen - they chewed on stuff of course but never to the point where I was worried or they destroyed anything (cept for my husbands eye glasses and that was HIS fault for leaving them in reach)
for such tiny dogs they can sure make a mess out of things we never think they'd bother with