I made the same door hinge mistake initially. The pictogram directions aren't the best.
For burn time, the only time I tried to see how long it would go I got a little over 5 hours at 275ish per Inkbird, on a basket full of post oak lump, empty foiled pan, 2 bottom vents cracked, one closed, top 1/4 closed. That was its second cook. The lump wasn't packed in densely, just dumped it in the basket, so there is room for improvement on that. Planning on doing a cook with briquettes soon, and will take note of how long i can make it last. Regarding the dome thermometer, mine runs about 30 degrees off from my Inkbird and Maverick probes. Don't remember if that was +30 or -30, because I quit looking at it and just use probes... No problems at all here with any of the probe ports.
I have been tossing a couple notions around for the ash situation, if any of them prove worthwhile I'll let y'all know.