I think at 4000 calories you are over estimating it, because if you were burning 4000 calories you would be able to maintain a 1500 deficit eating 2500 calories and lose 2-3 lbs per week. But you were only eating 1500, and had been losing 2-3 as you say. So I think your calories burned is probably closer to 2500-3000.
The formulas don't take into account fat/lean mass so they are not always accurate.
Its not that 1 day of 1500 extra vs spreading it out over the week is better than the other, but when you put the extra calories and alcohol intake side by side they are a bad combo. Also when you spread it out you are still in a deficit everyday, whereas on the 3000+ calories days you are going into a calorie surplus possibly storing fat, so its counter productive.
Try to reserve the alcohol for special occasions and try not to reward yourself with food or alcohol.
And I also just think you could maintain your losses with a little less of a calorie deficit, if you added in a little more exercise.
It's lack of faith that makes people afraid of meeting challenges, and I believed in myself. ~Muhammad Ali
You must have long-range goals to keep you from being frustrated by short-range failures. ~Charles C. Noble
July 6th 2010: 225 lbs, 24% body fat
Nov 30th 2010: 181 lbs, 12% body fat
Dec 28th 2010: 177 lbs, 11% bf
Total weight loss 48 lbs.