I like the changes you made. It's still relatively easy for veteran players, but we need more holds geared towards newer players.
One room you might want to take a look at is 3S. Those two plain blobs of tar in the upper corner are a bit on the ugly side. Putting something in them, pits for instance, might make the room look better without changing the rooms solution.
Also, as Stefan mentioned, the orb in the boss room no longer does anything. If it's possible to kill all the serpents, I don't see how. If there is a way to kill them, then kudos for stumping me.