It sounds alot like a high moisture content in the charcoal to me. Typically a slow start followed by a huge blast of heat then an endless fizzel...
Even with perfect coal arrangement if they're never snuffed you'll have several incompletely burnt coals left on the fire grate the next day.
Otherwise:
I havent used brickets in several years but IIRC you should have a solid 30-40 minutes of prime cook time after you dump your load. Less if the coals were rageing in the chimney till they all turned white. After its past its prime itll never gain heat again, the temp will only gradually fall.
You burnt some of that time sanitizing + 10 minutes choking. so there were less than 20-30 minutes left of your charcoals prime ability after that. Which is questionably enough to time to do a really good job cooking a full grate of fryer breasts.
Choking the coals can kill some of them permanently, especially when they're spread thin, and they'll never relight without catching fire directly form a heat source after that. Like contacting an ember or flame.
When your cooking (especially with a full grate) there will be juice dripping making steam & smoke that tends to fizzle your sizzle a little more. At this point the O2 level in the grill is way low and the coals are getting a shower. Any meat enhancement is working against you too.
All the previous posts offer workable advise. IMO.
The core of your cookout is based on your fuel because the kettle does a great job helping you manage the fire, so the learning curve there is minimal. As far as the fuel goes, if you make sure it can burn to the best of its ability before its lit you'll be aligned with success from the start. All that is required for that is good DRY charcoal & a bit of fire management. How & where charcoal is stored makes some difference in how it'll perform. My best advice for your charcoal is to store it off any dirt or concrete floors, on a pallet or other wood runners, that allow air circulating all around. During long term storage charcoal will practically pull moisture from those surfaces through the bag. Always keep your bags closed and/or lightly covered, a wide open bag will absorb moisture in the air almost as fast as it would if you threw it in a lake. Keep the bags away from any appliances like washer, freezer or fridge. Since your in the great white north it won't hurt to store a bag in the house for a few days before you start using it, maybe cut a small hole for evaporation if you thinks its really moist.
IMO starting with dry fuel gives the best results because it can perform to its best ability. You'll get more heat, more consistent burns, more even liting and better predictability from dry char than moist.
Part of the job of fire manager is to make sure the char can burn efficiently and effectively. To do that is simple all you need to do is arrange the char so there are no gaps in the coal bed where the coals aren't contacting other coals. If the coals aren't touching its highly unlikely the fire will jump from one brix to another. Lit charcoal will never meet its potential if the coals cant use air drawn into direct proximity by other lit coals, in effect bombarding/stoking each other.
On your next cookout try covering @3/4 of the fire grate so all the DRY char is forced to contact. It dont all have to be lit as long as its contacting. You'll automatically have your "safe zone" that way and some extended burn time too.