I'm an estimator, too, have been for the year I've been on my plan. I likely don't have it down to a science, but the thing is, who cares? I'm happy with my weight loss thus far, and I'm getting very good at scaling back a little if the losses stall. So I say, if it works and you are satisfied with your losses - then you are doing it right! Also, I have a cabinet full of measuring cups and spoons if and when I get to the point that I'm not happy with my progress.
As far as the craving sugar thing goes, I'm very careful with this. I used to not allow it at all because I can get a vicious cycle going with it as others suggested. Sugar begets the desire for more sugar for me. However, I know I will want a dish of ice cream now and again for the rest of my life, so I have been "practicing" with it. My daughter and I go for ice cream every Friday, taking turns picking the place. I look forward to our ice cream adventure every week, and I find it helps me to make good choices during the week that I have my ice cream waiting for me. WHATEVER works for your mind, body and spirit, I say!
When it's not my ice cream day and I'm confronted with a plate of brownies at work or an odd craving for candy, I try to think to myself "Will having a couple bites of that SATISFY me, or leave me wanting the next bites?" Usually it's the latter, so I pass. Sounds like your 1 1/2 servings did the trick. Do be careful not to go too low on those daily calories, though!