This is one of those things where it's better to find a way to avoid the problem than to get him to stop. Get rid of the stuffed animals and only give him sturdy plastic ones. As far as beds go - you can get a Car bed or Thomas bed that encloses the mattress and there are plastic mattress covers and I always do repairs with duct tape when I don't want to replace a mattress right away. You could try ditching the mattress and giving a sleeping bag a try for a time. You could find a way to cover the actual top of the mattress with some kind of cover made from tent material or something really sturdy. You can also put the animals up on high shelves and only allow them to be played with at certain times when you are supervising.

my son does this to stuffed animals also he has gotten better bout it after seeing how flat his fav bear was, and the most recent was a bean bag chair, i went to wake him up and it looked like it had snowed in his room, when i woke him up, he had it in his nose and a circle of it around his mouth, i told him it looked like it snowed, he told me very seriously,'it does not taste like snow' he just cant help himself.

I know when my son was little he loved to play in bins of rice and a table top glob of shaving cream. It probably helped him fulfill his sensory needs in a less destructive way.

my son has autism and when he was younger he did the same thing but he did it because he wanted to see what was inside and he would destroy alot of his toys but it was to see how things work so we would buy him dollar toys to keep out and his more expensive toys we would get out when we could watch him and put them away after he played with them for a while