Not being a doctor I wouldn't make recomendations re: fasting with health issues.
I will tell you that back in the late 60's and early 70's I was hospitalized for a bout†of Ulcerative Colitis.
After being treated with with drugs for a few days the doctor said I should have the offending colon removed. I would then have to deficate in a bag that was attached to the remaing colon and hang outside my body.
There was no way in hell that I would agree to that. I was still young and very active, not only that, but lived you might say a little on the wild side.
Anyway I told him no way, and read a book "The miracle of fasting" by Paul Bragg. I did my first 10 day fast and ran about 3 miles a day, plus exercises. Never bothered by the "UC" again. Had so much energy I was working every day and when I got home couldn't find enough things to do to satisfy my energy. Since have been on quite a few fasts the longest 30 days.
Would the same thing happen with you? I can't tell you that, but my gut feeling is that if you started a little slower, like 1 to 3 day fasts, then eat 1 to 3 days, [off and on] until you could feel confident with longer fasts, and hadn't had any issues with your present health issues you would be alright.
You do need to drink distilled water, but you can by it by the gallon for around $2.50. There are certain nasties in some water that just "filtered" water doesn't remove.
Also Paul Bragg said that people that didn't have weight to give up during a fast shouldn't worry because your body will adjust for that. That's another important point. Always listen to your 2 brains [head and Gut]. Don't hesitate to stop your fast if you have any problems. You can always start again. Some look at fasting like a marathon, "the longer the better", don't go for that.
If you attempt to take any viamins, etc. while you fast, you are no longer fasting. As far as your calves, you didn't say what the problem was, but if it was cramps that's an indication that you need Magnesium. not while you fast.†
Sure you can ask questions. somebody will be here to answer them if they can.