The only thing that changed is that once creating the flight in the FSX free flight window, under "current location", I dont see anymore the "Houston Helipad" (although using ICAO KIAH) but now I see the correct airport name "Georg Bush Intercontinental/Houston"
It's not possible the FSX free flight window would be affected by your change in the Couatladdons.ini, since that file is used only by GSX, and FSX doesn't know anything about it. In fact, your screenshot of the Create Flight windows clearly shows the Helipad is still there, but this is normal and won't affect GSX in any way.
However, once I upload the flight, GSX still has in the airport settings the AFCAD of the Helipad i.e. JFKH
The only possible reason of GSX still showing the helipad are:
1) You haven't restarted FSX or Couatl after you modified the Couatladdons.ini to add the exclusion.
OR
2) The AFCAD is *named* AF2_JFKH.BGL, but the helipad ICAO is NOT defined as "JFKH", but as something else, which would explain why the visibility command didn't had any effect, since GSX use the ICAO in the AFCAD file, not the filename, which can be anything and might not include the ICAO code at all.