How much weight will I lose running 40 minutes a day, 5 days a week?

I am 5'3, 55.5 kg, female and I want to go down to 53kg as my ideal summer weight. My body size ratio is Chest 32", waist 26", and Hips 33"...I want to lose an inch or two over all!

I have started running between 40-50 minutes a day, on 0% Gradient, but between 9-11 KMPH, on a treadmill every day. I do a jog/walk/jog/walk to keep my heart rate up. I managed to get down to 55kg after 4 days of running, but yesterday, even after a 700 Calorie work out (500 in the morning, 200 in the evening) and eating my net calorie of 1300, I went to the cinema and had a pack of pick n mix sweets, which probably took me over 2000 calories! Today I weighed myself and I'm 56.2 again...and I feel like all my week's effort has been in vain, and now I have to do another week to lose that half a kilo! Why is it so much easier for the scales to go up in numbers? I don't even know if I'm eating correctly, sticking to my BMR etc...I am not good with the macro (fat/carbs) counts...but I do eat healthy...I never ever eat fast food, I eat a lot of fruit and veg...I eat mostly grilled food...my only downside is that I love nuts...and sometimes the occasional sweet or chocolate (like last night!) ...

Will I lose weight if I carry on the diet/exercise regime I am on? Sticking to a net calorie of 1300...(Without ruining it with pick and mix of course!) , I would do weights, and I know it's a great way of building muscle and boosting metabolism, but the idea just doesn't appeal to me! Thanks!