In the Forgotten Outpost, there is a pressure plate to remove one of the walls.
Facing the broken door, if you could move forward and turn right, you would be looking at the removable wall. Just follow the path around to the end, and look for a pressure plate on that wall, in the line of seemingly decorative bricks/stones.
The skill book should be on a chain near where you start (if you used the scrying stone yourself). From the weapons, it is to the far back on the left, and you may be able to see part of the chain over the wall/column there. I have not gotten that far yet in DKS.
Magic is still over-powered. The magic damage enchantments on weapons also get applied to spells in DKS, so duel wielding is highly recommended (no points in the skill required; the off-hand penalty is not taken into account for spells).
