So, because I still don’t have a composite out cable, and limited access to a HDMI monitor, I have to do something else to keep testing.
External display over ADB (usb) is now working after a lot of fiddling.
It works via MyMobiler in 640x360x32, so very small.
Mouse doesn’t work, but keyboard works.
I’ve tried Androidscreencast as well, in combination with the Android SDK. It has much higher resolution but only 1 FPS, so pretty much unusuable.