Advice on toilet training/separation anxiety

Hi All,

Looking for advice on toilet training.
We got our rescue dog a couple of months ago and he has never gone to the loo in the house. Today was the first time he decided to do his business on the mat in the spare room.
Now he is walked twice a day as well as access to the back garden regularly- on the walk last night and today at lunchtime he didnt poo...I was thinking it was a bit odd but gave him lots of opportunites to go in the garden etc, but with the rain he didnt seem to happy about having to go outside!
I know accidents happen but I am wondering how I should deal with this, I really need him to know that when we go outside he has to go to the toilet. He is on a regular feeding schedule and I am home all day with him.

Also when I go out he is kept in the kitchen and inevitably he gets at something and destroys it. Not every time but he seems to get very distressed when I leave. Last night I was going to the shops and my hubby was here with him, played with him for ages and loads of attention etc, he went upstairs for a shower and I came home, the dog was after getting at a cushion and the stuffing was everywhere. Hubby said the dog was agitated etc as soon as I left. Has anyone tried the kalm aid stuff...does it actually work? I am not working at the mo so am here all day, even if I go in for a shower chances are he will get at something and chew it, even though he has lots of toys to play with. I have started closing off rooms and putting stuff away that I dont want him to get at but its a bit more difficult if its the kitchen chair he decides to eat!