I already expected you were no racer
, that is why burning 1000+ cal/hr is a very big overestimation.
Without being to scientific about it I expect you to be able to do between 350 and 550 cal/hr at a pace that makes you sweat and breathe hard.
There are a couple of things wrong with your calculations. Lets concentrate on 1 figure, eg:
42mins 18km avg HR: 117 Calories: 784
Based on time/speed/weight/age the calories should be: 771
The average speed was 25.7 km/h, on a flat with no wind this requires 130W and for 42 minutes that gives you something like 315 Cal, not 771. So I don't know what you are using to calculate calories based on speed on the bike, but it seems wrong.
Another problem is that doing 25.7 km/h on the trainer might not be the same effort as doing it on the road, which is what the calculators are assuming, but it could be that your trainer has been calibrated to give a realistic resistance based on speed.