Extremely intermittent separation anxiety?

If I were you I would at least try to put him in a "safe" room. But I am thinking, give the crate training a try. Most dogs really don't have that many issues with this, and it encourages them to just sleep during the time you aren't home.

As for the cause if his anxiety attacks, it seems like maybe something from outside (a noise, thunderstorm, etc) might be setting him off. Of course that might be hard to confirm. But if you found out what it was, it might help you with a solution...

to be honest, for *me* I crate my dogs while we're gone just for that ONE time that it may prevent disaster.  This probably is *not* separation anxiety -- that happens all the time.  This is probably being triggered by something or someone - either someone doing something deliberate, someone at your door, or some particular "thing" that is wrecking havoc and upsetting the dog.  Not knowing you it's hard to tell since we don't know you well -- but it could be someone at your door, window, an animal outside.  But when it does happen either it's of a long duration or it so completely unnerves the dog that it has all sorts of other ramifications.

The problem is -- this kind of destruction can be harmful to the dog.  Swinging on vertical blinds, drapes can pull the whole assembly down on the dog and injure it. 

 A friend of mine lost two dogs -- they were playing while she was gone and somehow pulled a television set off a stand -- the explosion of glass injured one dog to such a degree he had to be put down, and the actual falling of the tv killed the other.  It was devastating. 

The primary reason TO crate is to protect the dog.  Dogs are den animals -- they see a crate not as a prison but instead as a 'safe place'.  You need to acclimate them to it -- you don't just shut them in a crate and then leave for hours.  You feed in there, give treats in there, gradually make it a 'good' place to be (and I always keep the crate in my bedroom -- it's a room for "sleeping" anyway). 

As long as you don't treat it like something that distresses *you* and he associates the crate with all things 'good' he shouldn't be miserable at all. 

I used to be adamantly against crating -- and then not only did my friend lose both her dogs, but I had 2 of my 3 dogs have life-threatening injuries because of not-crating them.  And I've crated ever since and have never regretted it. 

It is we humans who have this "thing" about "losing his freedom".  That's not a dog concept. 

I tend to agree that this sounds like it may be related to something outside the home vs. true separation anxiety.  Common causes are those mentioned above, plus construction noise, changes in routine (are those few times a year related to odd hours at work, coming home for a minute and then leaving again vs. staying home for a while, etc.), emergency vehicles, people next door carrying one, etc.

If your dog has issues with the crate, you can try conditioning him to it, but I do have one dog who cannot be crated due to anxiety issues, so if she needs to be confined for some reason, we use baby gates to section off a safe area.

If I were in your shoes I'd be trying to ID the trigger so I could desensitize to that vs. just confining to minimize damage.  It's always better to determine the cause of the anxiety imo.

 I know it's a pain, but it might help you to set up a video camera.  Dogs with separation anxiety will generally exhibit their destructiveness fairly immediately after you leave, while a dog that is being triggered by something else will be more likely to exhibit the destructive behavior in response to the trigger.  Videotaping can help you identify exactly what triggers the behavior, and then you can construct a desensitization program based on your findings.  Crating is not the only solution, as some dogs will injure themselves quite severely to try to get out.  Take note of the places where your dog is destructive.  The SA dogs usually are most destructive near doors and windows in an effort to get to you.  Dogs that just shred random things, not so much.  The urination, defecation is often related to the fight/flight mechanism that dogs have - something tells them when they are stressed to "lighten up" in case they need to beat feet outta there.