FB HR is notoriously off, if you want to use HR in your training/calculations, get a real HRM with a chest strap (polar would be my suggestion). also, HR gets high during weight lifting but the work/effort required by your body is different than it is for cardio. using HR/calories burned during heavy lifts is inaccurate, only way to get a more accurate reading during lifting is circuits - low weight, high reps, very short rest - if any at all, preferably some cardio or plyo in between (step ups, box jumps, jump squats, jump twists, burpees, sprints, etc)
no wonder you dropped so fast, i'm a chick and 1400 is extreme for me - @ 1500 i was losing 3lbs a week in the beginning.