My approach was like yours, a complete immersion into the healthy lifestyle. A make-over to establish healthy choices and self-mastery.
I am your same height and started at 185 pounds , it took me a year to lose those extra 50 some pounds. It was a good rate of loss that allowed my skin to tone and tighten as I lost. I also learned a lot about patience and perseverance while I ingrained healthy choices.
I did a web search on calorie needs for nursing women and this sounded like the average answer...
"Pregnancy and breastfeeding increase the
need for calories and most nutrients. A
women who is pregnant or breastfeeding
needs to eat 300 more calories to provide the
extra energy thebodyneeds.Remember,this
is not a lot of food.
I have found in my 9 years of maintaining that around 1350 calories a day is what keeps my weight at healthy BMI. I average an hour of cardio in the form of brisk Kangoo Jump walks and road biking every day.
With our (5' 4" women) suggested calorie range is 1200 to 1500 per day it seems like your correct range while nursing would be more like 1500 to 1800 a day. We are all unique and maybe more calories is what works for you but 2400 seems high to me. Do track no matter what the number comes out to per day as this is how you can guage how you need to adjust for you.
Blessings to your new baby!