I had this and it did get better. I also get quite grumpy particularly if I have overdone the carbs and booze on a non fast day. I was drinking lots more tea and coffee also which I think affected my sleep.
Weighty What is your TDEE? Just thinking laterally that if you - while you get used to fasting - take your fast calories to 25% of TDEE (if its higher) also, think in terms of 16:8 (eating between noon and 8pm)
what was your 300 calories? as the type of food makes a HUGE difference to how quickly you get hungry again afterwards vegetables and pulses - ideally in soups or stews are the slowest to digest so will keep you not hungry for the longest also, try to save more calories for the end of the day .... around the 450 mark this www.waitrose.com/shop/ProductView-10317-10001-135557-Waitrose+LOVE+life+italian+bean+soup is 330 calories for the whole pot ....
eat later in the day on fast days .... I do not have breakfast or lunch - just lots of tea and water - and then have my 500 calories in the form of vegetables (soup normally) around 7pm then sleep like a log ....
the headache implies dehydration rather than hunger : have a pint of water before going to bed as well
fasting does not 'make you grumpy' : it destabilises your system and you need to find other ways than food to restabilise it
2nd fast yesterday and I'm not enjoying it at all. I woke up at 2.30 famished and with a headache so in the end got up at 4.30 had a piece of toast and paracetamol. The first day I also woke up earlier than usual. Not sure how long I can carry on like this for. The fasting also makes me very grumpy!