Good sound arrangement. I just think that when the kick and percussion elements that have a lot of punchiness to them sorta collide with the sub bass. A way you can fix this is by tweaking the levels, maybe make the sub bass less low endy, cut some of the lows out if you can. As for the punchy elements like your drums, you need to keep that for dubstep. But I just think the bass is a bit too harsh in the mix in my opinion. Otherwise you did really good at nailing a great dubstep sound.
To sidechain, one wire of your kick should go into the centroid and the other one to the sidechain input. You can practically use anything for the sidechain input if you want to, it doesn't really matter. What I like to do is use the tinygain for the sidechain input.