captaincpfd, it gets better. They are right. Yesterday I had 175 gal of sap to boil. First boil of the season. On my 3x8 I started to boil with about 1.25" in each pan. I quit feeding the fire when I have 18 gal of sap left in my feed tank (a clear site tube teed into the feed line with marks I made to know when to quit feeding the fire.) I was just getting close to first draw when shutdowm time came, hence no syrup yet. Will not boil until likely Saturday. It will just wait because temps are too cold for sap to run.
As for burning it you must have gotten too low sometime. As you gain experience things will get better. I suggest you make some sort of feed line and start with a mark at lets say 5 gal as when to stop firing. Let the rig stop evaporating and see if you have more sap than needed to keep your desired depth. To learn 2" is good, as you get experience you should slowly lower the depth til maybe 1.25 or even 1" deep. The shallower the faster the boil AND the faster problems need attention, just get good at deeper and over several days reduce depth. As for only boiling in center, some questions. Is your rig outside with cold air hitting the sides? Is your arch insulated or firebricked? When I had a 2x3 size I found it best to fire every 6 minutes, split the wood wrist size. I now fire every 5 minutes. Give it all the air it will take. Now for the best part, you have burned a pan so by definition you are now officially a syrup maker, and you got it over quickly!