Follow richards recomendations about the hopper height. After looking at the blow up of the stove, down low won't give you enough depth at the front tof the fire box. I'm using Reading pea, and the ash is stiffer that what I used before, so i had to raise the hopper throat up as higher to have more weight of unburned coal to squish the ash more for better feed and deeper fire mass (longer burn time with less burn back) I think you want to shoot for as high a coal level at the front as you can get, like Richard says.
I still think you should be able to get 8-10 hours of moderate burn levels . Granted my hopper and grates are different, but on my smaller resolute, I have to shake more than the vigilant, to keep the same higher burn levels. I don't understand from the blow up how the grates shake, mine rock, but I have the ability to slice across the grates with a long thin slicer "knife", and have to do that to really clear the grates for a high burn.
maybe richard can tell you about the franco, but after a 8-10 hour burn un tended, the coal in my hopper is only half empty---- till I shake and slice, clearing the ash and then the hopper is usually empty, but fire box is full. Running with the thermostatic flapper open after that for a while, the fire revives to a bright burn and I fill the hopper, set the thermostat back to where I had it and I'm done.
Sounds like the baro is cutting your draft OK, I think your biggest problem is a shallow coal depth because of the hopper height.
I tried some Blashac coal ant it seems to have less ash and a lighter less crunchy ash than the reading, and the hopper flowed down better-- more contant heat over time-- so next year I'll get blashac pea.
As for pounds per hour thinking, the way I look at it is if ya figure around 10,000 BTU per pound burning in a stove rated for 50,000BTU, 5 lbs per hour would have me stoking every 4-5 hrs on a really high burn, cause my hopper only holds 20-25lbs of coal (above the fire mass). This would be at a stove top temp of 700 or more I bet--- unrealistic, and a lot of work!! So my overnight burns that dump my hopper after shaking ( 8 hours elapsed time), and taking 20-25 lbs to re-fill, I'm only burning at about 3 lbs per hour--- averaging approx 24,000 BTU/hr. This scenerio is for a real cold night, starting out at 450-500deg at night. lows around 30 around 375. All this heats the house fine, but I'm doing it on 2 stoves at each end of an ell shaped house upstairs.
Sorry for the long ramble, keep us informed!
Keep at it, you'll get it to burn more more than what's in the active fire box I'm sure.