Cool map, buddy.
I think it had a lot more potential than what was fulfilled.
I'm going to copycat Pottus here for a bit:
Layout - 5/5
Texturing - 2/5 - this is 110% personal preference, because the texturing is certainly GOOD, but it's too reminiscent of a lot of other maps I've seen in Doom. For being a creepy Halloween map, I did nothing for me, I'm afraid - it was all too familiar. I'd kind of wish you used the flat for the exit room in map01, as the landscape texture for the rest of the map, and change everything else accordingly. IMO, the texture style is cool and all, but it also has a great deal of randomess in it, if you ask me. I don't really like it, but I may be in the minority on it.
Lighting - 2/5 - it was pretty bland, and especially for a Halloween map. I did use GZDoom, though. There is no problem with unusual light levels, in my opinion, so long as you've evaluated it to be appropriate.
Gameplay - 3/5 - it was cool and interesting, but it had a lot of unfulfilled potential, IMO. I'd like to see more Arch-viles, because you were very careful with the monster placement, so if you had handled Arch-viles with the same care, and with the same minimal monster count, I think it could've been really cool.
Overall, I think you are great with layouts, and that, like everybody else, you have something to work on, and in your case I'd say it's lighting and monster (and weapon) balance for the best gameplay that YOU desire.
I read some impressions before playing, so I saved shells and it went okay. But if it's supposed to be atmospheric with a build-up, then starting with a DOUBLE-barrled shotgun is perhaps not the best route.
Regarding texturing, I think it could've been a lot more atmospheric and ORIGINAL, if the theme was something new. But then again, I've played Doom for quite a bit :)
Finally, thanks for the map. It was fun to play, and it was fun to write this post, hehe.