I agree, I think that is a great cook, especially given it is your first packer cook, it had the charcoal problem and you over-slept. You really can't leave it in the cooler too long, but, you could have done a little less time in the oven. Quibbles man, quibbles.
Although I use briquettes, I mainly use Royal Oak or Lazzari, sometimes Kingsford. I have never had what you describe. But, I have seen charcoal that looks lit end up being burned out, that kinda sucks. Still, a good hunk of meat.
In terms of temperature, I am also part of the converts to hotter temperatures, between 280°F and 300°F for me, in a UDS. (incidentally, 225°F=107°C, 325°F=162°C). I learned to cook hot 35 years ago, then forgot, and switched to the magic 225°F number and struggled with consistency, then came here 5 years ago, read Pitmaster T and Saiko and changed back to how I learned. So much more consistent.