You can use Nvidia surround thingy to make the game run across multiple monitors.
If you are worried about the clutter, 3DX added the ability to hide the action menu from being visible not to long ago.
Also you can use the shortcut shift+z to hide the UI of the game.
False positive only reported by Kaspersky.
Kaspersky has been notified about the issue, and the false positive will hopefully be sorted out soon.
Add the GameAssembly.dll file to exclusions, if you can't do that you could add the entire folder until the issue has been resolved.
For world editor, read the documentation:
For the "confusing buttons" go to options (Press F1) and enable the text (is activated by default, last I checked):
For any other questions, maybe read the tutorial:
Late response: Also try to disable OneDrive, it might cause the game to launch, but go into a load loop before giving you the character selection window.