Congrats on decided to take your life back! That is a huge step in the right direction.
I think it would be helpful if you would list the foods you are eating and at what times you eat.
Try to eat lean proteins like chicken, fish, lean beef, fresh or steamed veggies, fruits, whole grains, oatmeal. Stay away from processed foods like crackers, chips, frozen meals, pasta (unless it is whole wheat), processed cheeses, white breads, etc.
I do think you need more calories to fuel your body before exercise. 604 calories is not much to go on - no wonder you felt weak! Eating a boiled egg is actually a good post workout meal, since it has protein in it. You need protein after a workout.
Don't worry about not being able to do much right now. It will take some time for your body to adjust to the demands you are putting on it. And trying for 60 minutes of cardio after not having exercised in 10 years was aiming a bit high. 15 to 20 minutes is probably good for now, and you can build up from there.
Try to incorporate some basic bodyweight exercises. Jumping jacks, Windmills, squats, lunges, pushups (incline or on knees at first if you can't do a full pushup), leg lifts (lying on floor and raising legs up approx. 6 inches and back down. Try to do 2 sets on each exercise, 8 to 10 reps if possible, just pay attention to how you are feeling physically.
Hope this helps some. Good luck!