I recorded a blind playthrough of your map:
https://www.youtube.com/watch?v=P4h99CgjJIA
I found a weird bug below the health pack (look at 00:47 in my video) in FTE engine the bug looks like a hom effect, in quakespasm it looks like a grey polygon.
About the gameplay, I have some thoughts...
I felt a little restraint in my moviments, there's not much free space to run and move around, every place seems so tight, mainly the walkways...
I think the final fight would be more awesome if you had released the zombies when the shamblers appeared. The way it is now, you can just kill the shamblers and go to the exit without killing the zombies, they are no threat to the player. And about the zombies in the second floor... there's any way to go up there? Killing them from below is just tedious. There should be a elevator or a platform :P
Oh, and never let the player leave the final arena. I could easily run away and kill the shamblers from the corridor. You should consider locking the door =D
But, for a first map, this is an amazing job. Congratulations! =D