Hi Kim & welcome

We're county neighbours, I'm in Dorset - used to holiday a lot in Devon when I was little

1. Often the packaing will give you an indication of the calories (sometimes it's on the back of the label, you can only see it when opening), but otherwise there are some great online calorie counters such as My Fitness Pal - have a look in the Resources forum for some handy links for calorie counting.
2. Fasting days should be around 500 cals for a woman, or a quarter of your normal intake if that works out as less (which is around 2000 cals for a woman, but this can be more or less depending on your activity level, height etc).
3. My Fitness Pal is supposed to be a very handy app, though personally I don't use any diet/health apps.
4. I don't keep track of my foods, I'm just more aware of the calories I'm consuming thanks to what I've learned through my fast day planning!
5. Add up the calories of all the ingredients (don't forget to include oil etc!). Weigh the entire batch, divide into portions and calculate total cals in the portion based on that. Eg I have a 'fasting lasagne' recipe I make which has around 1800 cals in the whole lasagne. It makes 6 portions (which I weigh out to keep them fairly equal) which each have 300 cals.
Hope that helps!