The map looks good so far, but I've had some problems. I got a lag spike when knifing a zombie, and a lot when I used the artillery strike. When I take a weapon from the box it doesn't give me it.

what is the code name for the map,
so I can use cheats to change my Fov

It's "deadfactory" the same name as in the mods list.

You have to run the other installer, it will always install in the New_Realism mod folder do it will overwrite the other map ( not your progress! ).
Close the game, run the installer for the map you want to play, and just restart the game..

It's a bit clumsy, but it works. and installing a map shouldn't take more then 1 or 2 minutes once you got it downloaded.

 I found a way to fix it before my comment went through, but I couldn't figure out how to delete it before it was approved (These are the first comments I've made on this site) but I just renamed the folder to have the map name in it and now I can just load whatever, I don't need to use the installer constantly.

Sorry if this is a stupid question, but how do I switch what map I play? I downloaded Der Riese first, and then got Estate and Nuketown but when I load the mod it's just Nuketown.