To see what you are talking about, I just hooked up my other display to my laptop.
I have to make my external display be the primary (by temporarily turning off the laptop screen), then I can place it on top of the laptop display & drag windows there. Of course, that makes gnome bar show up on the external. I think if it's on the lower (laptop) screen, it's what preventing you from moving windows up (I tried too).
As to your monitor not being detected properly, I ran into the same problem when I tried to use a VGA extension cable for my external display (I think I need an XVGA) - which is why I don't have it hooked up to my laptop normally.
Here's the output from xrandr in this configuration (but I used Settings, Displays) to set it.
Code:
Screen 0: minimum 320 x 200, current 1920 x 1848, maximum 8192 x 8192
VGA-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.0*+
1680x1050 60.0
1680x945 60.0
1400x1050 74.9 60.0
1600x900 60.0
1280x1024 75.0 60.0
1440x900 75.0 59.9
1280x960 60.0
1366x768 60.0
1360x768 60.0
1280x800 74.9 59.8
1152x864 75.0
1280x768 74.9 59.9
1024x768 75.0 70.1 60.0
1024x576 60.0
800x600 72.2 75.0 60.3 56.2
848x480 60.0
640x480 75.0 72.8 66.7 60.0
720x400 70.1
LVDS connected 1366x768+0+1080 (normal left inverted right x axis y axis) 344mm x 193mm
1366x768 60.0*+
1280x720 59.9
1152x768 59.8
1024x768 120.1 60.0 59.9
960x720 120.0
928x696 120.1
896x672 120.0
800x600 120.0 60.3 59.9 56.2
848x480 59.7
700x525 120.0
720x480 59.7
640x512 120.0
640x480 120.0 59.9 59.4
512x384 120.0
400x300 120.6 112.7
320x240 120.1
HDMI-0 disconnected (normal left inverted right x axis y axis)