hi there. putting on 6kg in a week is not right. Get to your doctor today. Given that you have CHF it needs attention and investigation. This is a really serious weight gain and if its correct, it will need prompt attention to prevent further complications. The doctor has all the history of your condition and it may be you need a change or increase in meds fairly quickly. god bless and let us know how you get on, but please go to doctor now
I think he needs to see his doctor. Leg cramps can happen when we are low potassium. And furosemide is also known for muscle cramping. I'd circle back with your doctor for the next step.