we talking 2" or a foot? Did you use backer board for the tiling?
The backerboard should dissipate the heat as with the distance from the glass. as long as there is some circulation back there it should prolly be ok
So I use a "dorm" fridge to do my fermentation in. I have a johnson a419 controller for cooling and the fridge stays in the house. But in the winter time I have a hard time raising the temp to finish off my ales. I don't have much space to consider with the carboy in there and I use glass...
I agree that there is potential for tannin extraction while squeezing the wort out of your grain sack.That pre-boil gravity would of helped determine your extraction eff.
Sparging with your wort is only going to increase the sugar concentration and thus make it harder to gain extraction from...
Yes the temperature was the culprit. CO2 diffuses into the beer more readily at colder temperatures.Thats why its best to chill to kegerator temp before applying pressure.
I just crank it until its a nice even flow and hold it there for about 20 secs or so. Anything crazy and it will start foaming up and out of the carboy
Always helpful to take all measurements and extensive notes for your first few so you can dial in your equipment..Big help when you run into problems. Don't get to hung up on efficiency its all about the consistency.