Listen to your own body
All I can say is: try to listen to your body and find out what works for you.
It is not so much important how many calories you consume, as much is important where those calories come from.
For example, raw eggs, raw vegetable, raw nuts & seeds provide great source of proteins, fats and carbs.
But is also good to consume cooked food like soups, broths etc.
While it will be easy to do cardio on Mondays, as you have been eating on Sundays, your ability to burn a lot of energy within a short time will decrease with every hour that has passed since you ate the last time.
You will feel it.
I think much healthier way to lose weight would be to go on all healthy diet, and maybe skip food just a few days a week.
That way you will have much more energy to exercise.
The main problem with Water Fasting
is that you may not heave enough energy to exercise.
Some people can exercise on no food, some can not.
Find out what is good for you.
Always listen to your own body.
It is not smart to overdo it, and end up in a hospital.
While water fasting, most people find it OK to do walking, yoga, tai-chi, qi-gong, slow swimming, slow dance, etc.
Few people are able to run, bike uphill, lift heavy weights etc ...
Find out what your body can take.