Why does he box walk, does he have enough hay, does he have ulcers, i would try and find out the problem for the box walking. Can you turn out in a ring overnight
I would also try to stop the box walking, the few box walkers i have known were worse in certain stables on the yard, one Arab I knew was terrible would have a track round the stable every morning, his stable was in a small square of stables with the road running at the back with no view of any fields so all he could see where other stables, I moved him to another stable with a full view of the fields away from the road and he stopped overnight, this horse also used to weave badly and that also improved, I also think a strict routine really helps, these horses tend to anticipate turnout and feed times when this doesnt happen the box walking starts, I would look at the management of your horse and his environment first.
I use wood pellets for my box walker, the bed is heavy so doesn't move around like wood chips etc do, it does start to look a bit bitty by the end of the week where she destroys her poos and they end up in tiny little bits, so you can't get them all out every time, but that will happen whatever you use, and the pellets are cheap enough that I don't mind losing a bit of bedding to get the little bits out at the weekend. Another added bonus is it's really quick to muck out during the week when I leave the wet in