From what i'm seeing, this game handles very much like Half-Life 2 or Garry's Mod. 
However, upon digging in the game files, I see the Unreal engine Crash Handler. 

What made you choose to remake Source physics in the Unreal engine?
Did you not have access to actual Source?
or did Source not have features your game needed? 

I'd like to know as I would like to get into game development myself.