What I meant is after every time you click on EDID emulation for the CRT display, you must regenerate and reinstall the modes. In your original post you were doing the generating/installing video modes before clicking on EDID emulation.
May as well just stick to generic_15khz profile for now.
Having said all that, the black bars do look like a problem with the sync (vertical). Looks like a cable problem!
The LED colour change is normal with the gambaman PIC based composite sync. LED changing means it is 'working'. I have a VGA-VGA dongle that filters 15khz and makes csync, made by @buttersoft, that is based on the same PIC used in your cable (AFAIK). So my dongle should work the same way as your cable.
It is possible that yours is having trouble properly locking onto the sync signals from your GPU. This can happen especially if the sync voltage levels are relatively low or quite different (between H+V). To investigate further you'd need a decent multimeter, or even better an oscilloscope.
Alternatively, it is possible to make your own SCART cable, run the H+V sync through resistors (~470R to 1k, depending on sync levels) and twist together to get "smushy" sync that will work for most TVs. You'd need some soldering and stuff for that, but at least then you could get a baseline for what works and what doesn't.