I only now noticed the comment about the fences.
I checked back to V3B Bombman since it was done in Hexen, and here's how you add fences in that version:
On the linedef you want the fence, give it action 121, Line Identification. After you do that, go to "Flags" and check the box titled "3D Midtexture." Then you just add the midtextures and you have your fence.
Proof of concept:
Now, I noticed there's one line horizon that still needs to be fixed in V1D Bombman, ironically the one that made me notice the line horizon issues in the first place. In the line of platforms leading up to the first place with fences, the next platform is still obscured. It should be immediately noticeable going through the map since it completely obscures the platform.
Fireman, is looking pretty nice. Now that the pit of inescapable death is gone, you could probably do well to widen that chute downward a bit just so it doesn't cause a stackup in multiplayer mode (most multiplayer servers will have players go through each other to avoid exploits, but it's still good to keep known issues like that taken care of just in case a host forgets to put that server variable up).
I want to ask you for the code you used to make the Killer Bullets, because I can't find it anywhere in your wad. Their coding is odd, to say the least, and I'd like to look at it.
Overall, I'm liking what I see now. You fixed the lift, have almost all the visual bugs taken out, and to be honest I think I'm running low on the advice I can give you since I'm not very knowledgeable on single player maps.