trying to figure out numbers..

Hello,

I've been doing lots of reading on the forums and have decided to up my calories to lose weight. I've visited all the different calculators and what not, but still don't have a good sense of what I'm doing, hoping someone can help me with the numbers.

Currently,
I'm 5'6, 140lbs, with a goal of 130lbs - but want to be leaner,
For the most part I cycle through Jillian Michael's dvds - Banish fat, boost metabolism, 30DS, Ripped in 30, Extreme Shed and Shred, No more trouble zones. So, I basically do 20-40 mins of exercise each day with maybe 2 rest days in the week.
I also work a desk job.
My body fat % according to taking on average on 3 different calculators is 25%.

So far, I've been eating around 1200-1600 calories a day and have been successful in dropping from 167 to 140, but I've hit a plateau and seem to be stuck now for the past two months. I think I may try upping my calories, but not sure exactly how it would work for me.

Basically, my question is on non-workout days how many calories should I be eating?
On workout days of only 20 mins how many calories should I be eating?
and on workout days of 40 mins how many calories should I be eating?

Or do I stick with the same amount of calories every day, no matter how long I work out for that day? Also, once I get to maintenance (hopefully over the next 2-3 months) how many calories will I be eating then to maintain?

I've been eating 1200 on non-workout days, and then just whatever the MFP calculator tells me to eat for the amount of exercise I've been doing, so for example, 1200 + 20 mins of exercise day (approx. 167 cal burned) I eat 1367. From what I've read, I should definitely be upping it, but not sure too how much.

BMR, TDEE and eating back exercise calories is confusing the hell out of me even after I read all the info, need help sorting out what I personally need to do since my workout routine changes every day depending on how much time I have available, plus like I said, I want to focus more on getting leaner now that I'm closer to goal.

Any help would be much appreciated!