Your assumption and consumption need attention. You have assumed a weight which is not correct, and you have assumed standard fuel consumption. In reality we regularly achieve 3.5 - 4 hrs endurance depending on wind and power settings. The perfect filming speed (when not hovering) is also the max endurance speed.
One of the great advantages of the 360 nosemount is that we can spend more time with our nose into wind - we regularly get the shot by shooting at 180 rearwards and, so long as the downward angle is more than 30 degrees, no aerials or skids get in the way.
With regard to POH and glide capability - we have made substantial allowances for wind, airspeed and other variables. An R44 can easily glide for more than a statute mile from 1500-2000ft. And the helicopter configuration for certification is at MAUW producing a glide ratio of 4.7 : 1.