Aarrgh! Chewing! Separation anxiety? What more can I do?

[MsAdorabelleDearheartVonLipwig]

Nearly every time I leave Monty in the house alone I come home to destruction. He doesn't do it when someone's there so I put it down to the separation. He's a year old lab.

Usually it's paper, someone's book, my shopping list, anything he can find, shredded to bits. Tellingly on the front door floor mat. He's obviously waiting by the door.

He's restricted to the kitchen, hall and living room. His crate and water bowl are in the kitchen and his bed is in the living room. He can reach the kitchen worktops but I don't want to shut him in the living room in case he starts on the furniture. I leave a radio on and he has a plentiful supply of dog chews, Kong ball etc.

I can't leave him shut in his crate, he's nearly outgrown it. Should I buy a bigger one and resolve myself to having to shut him in every time I go out? I'm not keen on that.

I have to do school runs, my help at the school, shopping etc. He's never left for longer than a couple of hours.

So bloody annoying. Our old dog never did this. Bloody creature.

My lab is 10 months and chews like crazy. I now keep a stack of different sized meaty bones in the freezer. I give him one or two each week and they seem to keep him going. Even when there's no meat left he'll be trying to get the last bits of marowbone out the middle so the bigger ones last him days.
He has every chew toy going but he much prefers furniture, walls etc. Blankets are his favourite so I now just give him one at a time to destroy and then I replace it when it's totally shredded. It's not ideal but it is focusing his attention on the one item rather than the entire house.
I recently bought him a crate but won't use it (even with the door open). He was a rescue and gets a bit freaked out at enclosed spaces.