Odd calorie consumption

I'm not familiar with Turbo Levo sensors. Is this a Ebike?

Yep. Specialized Turbo Levo. Power meter takes account  only Power of the pedaller. 

When I installed a power meter I was surprised at the drop in calories. They dropped about 45% from when I only used a HRM. Using a power meter is the only accurate way to get calorie consumption.

As a rule of thumb, 400 kCal per hour can be assumed for a fast trip (HR zone 3-4).
800 is in any case too much for 1:10h with ebike - imho.

Feels like a really small figure as I’m moving a quite a big mass. 

Ok, that looks really different to my estimation

Yep. Over twenty kilometers on rocky path is not an easy task in an hour. That’s why I’m a bit skeptic with the figure. 

I was just checking the calorie consumption for my last twenty rides. On a hard ride in the upper heart range, I'm only burning about 25 calories per mile. I guess converting that to kilometers would come to about 15 calories per kilometer. I'm a old guy weighing about 83kg so I would expect a lower calorie number for me but in you case I would expect somewhere around 20 per kilometer.

Perhaps if you could borrow a non Ebike with a power meter you could get a more accurate number to compare.

whats your max hr, what hr avg can you hold for one hour?