1200-1500 is all I allow. The idea is to count up for the week and have calorie average for the week. I use MyFitnessPal to keep track. I have only been doing it for 8 weeks so I am new at this too. It is working and it does get easier. I sometimes do a 3:4 of 700-800 calories. And it works the same.
This sounds like me when I am doing 5:2! I have a very active job and up from 500 to 800 with eating windows. I also tried to aim for about 1800-2000, rare over 2000. But it meant I could have waffle house occasionally and not worry. Although when I am in the groove I would have some days of just 1400 by accident. I can already tell my eating windows are having effect cause I couldn't finish everything at dinner that I logged. This was happening the last time that I was fasting and staying true to my eating windows.
I am probably going to start into 5:2 this week. I have been doing just eating windows lately. Even staying under my calories has helped me stay the same/lose, so far so good.