First of all congratulations on your weight loss so far! That's amazing.
Well, I am no expert but I think you're way overestimating on the calories burned. I don't know the weight you're at now but I think you would have to be walking at a brisk pace for many hours to burn 1200 calories.
I think you're probably in a great spot eating 1200 calories a day and losing 1-2 lbs. per week is great, especially if you're close to your goal weight. It sounds like you're on the right track and maybe your wish to lose more isn't realistic. Even at your current weight loss you could definitely make your goal by the end of the year.
And, the odd gain of a pound just seems to happen sometimes...my body is a mystery to me in many ways!
There are a lot of great people on this site with a lot more knowledge than I have. I think if you wanted to post a sample of your daily food, maybe people could help identify ways of improving.