I personally don't think it is a good idea. You have a lifetime of bad habits and several health scares recently including a possible heart attack. You are in no condition to undertake such an extreme program. It would be like you going out to try to run a marathon. I would start by trying to add some moderate exercise like walking and healthy eating to your regime and then maybe build up to a juice fast of a couple of days, then build up to a juice fast of a week, and then when you are making good progress consider a Water Fast with supplements (although I personally don't think an eight week one is healthy or needed). You are trying to do too much to soon. Concentrate on trying to make slow steady progress and stick with a reasonable program, and accept that there may be days you break it and cheat but be willing to start back up and not throw in the towel.