focus problems

The main config in ~/.fvwm/ is .fvwm2rc or config
From the FAQ:

So open the config in an editor mark all and paste it between the code tags.

To change it to a single desk search for DeskTopSize and change it to DeskTopSize 1x1
Another thing you can do to stop switching is, search for EdgeScroll and change it to EdgeScroll 0 0

Hmm, don’t know how VNC have to be configured. I don’t use it. So can’t help.

Part of Archwiki about .Xdefaults:

So this file is used for x applications and the behaviour of the x-server not for a window manager.

Don’t be angry if saying this but perhaps you should do more RTFM to understand how Fvwm is working and how it is build on. Here some start points]http://zensites.net/fvwm/guide/[/url]
http://fvwmwiki.xteddy.org/
http://fvwm.org/doc/unstable/index.html

Best,
TF