I am glad I picked this up. Usually I despise playing most Source mods but this was fun and seemed well planned and well executed. I love the bsp geometry, since I am a mapper too and I fell in love with a lot of the designs you came up with immediately. I do have a few things to suggest and point out as for what I did notice...
So upon extracting, I have to move all of the assets in your package directly to my folders where they go in ep 2. So that was a bit of a hassle. Not worried for just trying it though.
The AI spawning (as a suggestion) could have been triggered in more broken up sets so that we don't have groups of six converging on you all at once.
Oh and you may want to add auto saves before fights as a note cause I died and had to completely restart.
Just some things to point out level wise, which are quite minor...
I know you know that the brightness can be toned down some on these sprites because you did in some other spots of the map where needed.
Also here you might want to think about making these breaks, more like breaks with revealed wood shards sticking out along the edges and what.

A note about the zombies in the shafts. It appears that early on you increased the health of them when you first run into them. But later on the zombies towards the end of the encounter have notably less health. Small, but just a balancing note. Otherwise great job, and I found it quite Valve like. You kept the map flow very interesting, and if HL 2 DM was a fun multiplayer game I would say convert this into a map for it. XD
Was taking a break from my own mod out of being brain dead, but this inspired some more thoughts.
