It's not difficult to get it working with just pressure. First set the cut to 0 kPa, then drive around and watch the pressure as you engine break (release throttle), the pressure limit should be set just above that. Definately set it below the pressure you have with idle on a normally hot engine, which you seem to have tried to do.
It's also important to have a good VE tune and good ignition timing at idle, the engine should not have tendencies to fall through easily without any fancy features turned on (like overrun and idle control). This can usually be fixed with proper VE and ignition tuning around idle are and there are some band aids, like "idle ignition advance control" and of course a real idle air control valve.
Just doing it with rpm cut/resume is probably an easier way out, and very easy to set up.