Newbie with Heat Management Issues

Finally got my Egg after years of wanting one, but never having a back yard. Following advise from the dealer, I have been grilling on higher heats to sort of season the ceramic and allow for expansion and contraction in the joints before I tackle some spare ribs this weekend.

Made simple chicken fajitas and grilled some up some pre-smoked sausages (from Woody's in Centerville, TX - which rocks). Had no problem getting up to 550 degrees quickly, and easily brought it back down with the vents.

Last night, I made cedar-plank fish. I couldn't get the Egg up past 200 degrees, even though I did the same thing as previously. I think that although I left the charcoal in a dry place with the bag closed well, the wood still picked up moisture, because, although covered, the bag was outside during some rain.

I threw in another lighter brick (BGE brand), and the temperature quickly came up to 500 degree, which I tamped back down to 450. Problem is that even thought I burped the Egg, I got massive flair up after about 7 minutes. Singed hair off my arm; singed the fabric on the seal. Durn near scared me to death, actually. There was a lot of juice dripping from some super-fresh, large patty pan squash I had in there, and the plank actually caught on fire (I soaked it for one-hour, brushed a touch of olive oil on top and on fish - per BGE cook book).

The food turned out fine, although with a slight ashy flavor, which I guess is from the blow back up the dome when I had the flare up.

Any thoughts on what I did wrong; how I can prevent this, etc. would be much appreciated.

My thoughts are to use up the rest of the charcoal I have on low and slow cooking, and then be sure to keep my lump really dry by storing in my climate-controlled home. Also, I will need to make sure the air holes are not blocked. Doesn't seem to be an ash problem, because I took out the small amount of ash that was in the bottom of the unit before using it for the fish.