Incredibly well made first map. Seeing a long ass map on the workshop is very refreshing. Enviromental storytelling adds a layer of immersion, which is always welcome. The atmosphere is very suspensful, having subtle dynamic music shows that you pay attention to small details, which is not something that most beginners do.

No one's gonna make a perfect first map though, so I'll also address some nitpicks of mine:

First thing I noticed is that there's some inconsitancy between door texture usage. For example, the only breakable prison door is the one for Mike's cell, while the rest are unbreakable, despite using the same textures. There are also some cases where metal doors have the breakable property, and some wooden doors don't have the property. It's best to keep wooden doors breakable and metal doors unbreakable, as that's what the base game does.
The level also feels too easy on hard, so you could reduce item pick ups on higher difficulties. The climax was also extremely underwhelming, a single palooka is laughably easy to defeat.

In conclusion. Great first level, but don't be scared to make your future levels more difficult.