My dog chews everything!!?

We have a black lab who is 8months old, he is house trained and is generally a good dog, but lately he's started chewing EVERYTHING, our kids shoes books, moniter, baskets, u name it he chews it. i just dont know wat 2 do wiv him, he doesnt listen 2 me only my partner who he obviously see's as alpha so in the day when he's at work he's a nightmare!! He's walked 3-4 times aday has lots of toys bones bought 4 him all the time. We keep him in the kitchen in his cushion bed at night hes walked 6 in morning, twice in the day and once late at night. in the day he comes in the living room and plays wiv the kids and is ok, but as soon as im out of sight he plays up, we dont let him upstairs because i dont want dog hairs and germs while the kids are sleeping they have enough in the day! He hardly eats either he has ONE bowl aday and eats half in morn and half at night is that normal? We tell him off when he's sometimes we tap his nose if he's been really bad like pooh's in the house or snaps at the kids. They are good wiv him but he is really quite random and changes his behaviour allll the time im really becoming impatient now and people keep saying get rid of him cos he's ruining ur home but i dont want to get rid of him, i do love him but i am starting to dislike him more and more when hes , it seems that if we tell him off all the time he's good and if we give him attention then he thinks he has the right to jump and pinch food of sides, he steal my daughters food out of her hand all the time but never my son, my son his 3 and daughter 2. Please give adivce i want to keep him but just dont understand why hes like this!!