I keep it in the driest cupboard far away from the stove or oven, and make sure not to use it over steam, that will clump it.

I put rice in with the salt and shake it around. I put in about 20grains and that seems to stop it sticking. I do it with my normal salt and pepper as well. Hope this helps.

I usually get a spoon or fork to try and shred it it sometimes works haha

Break it up into smaller containers and stick rice in the containers. I know you will then have to sift it out when the time comes, but it will draw the moisture out.
We used to have it at a cafe I worked at. And in the shaker we would put rice. When the shaker ran out the rice would be left in the shaker, and we would discard and add more to the next lot. Never had an issue. Good luck,