I don't have time to read the whole thread here, but as someone who went from weighing about 315lbs. to 160lbs., let me be the first to say that it's absolutely doable. Be prepared for it to take forever and a day though! I lost that weight over the combined course of about 3 years (50lbs. one year, then I maintained that for a few years, and lost the rest of the course of the last two years).
A few things I can suggest based on my experience:
Do not eat too little. I'm serious. I've been there, and done that. It genuinely does make losing weight harder, and makes you feel like absolute crap. I wouldn't eat any less than about 1700 calories per day.
Eating a better balance of nutrients is a good idea. Veggies and lean meat like fish (not fried!) and chicken (not fried!) will help put a dent in the calories up front, and make a big difference. I'd also take this opportunity to try new foods. I learned to like a lot of new foods during that dieting period.
I never really got into taking vitamins, and I don't think it really made any difference. Probably couldn't hurt though.
Exercise is a good idea, although the vast majority of your calorie deficit will just come from dieting. I wouldn't try strength training much though, if you were considering it. After the first couple of weeks I stopped getting stronger and started getting weaker. I might have just been overdoing it, but I ignored advice from others that your body is bad at losing weight and gaining strength at the same time and had to let my body prove them right. After a few months I felt horrible constantly, and only felt better after I stopped. If you do plan on strength training, keep it low key and focus on aerobics.
Last, but not least: you're going to be in this for the long haul, so don't get in the diet mindset or you'll never stick with it. One thing I found that helped me tremendously is that I still mostly ate what foods I wanted. I just ate less of them. I mixed it up with healthy stuff like baked fish and fresh vegetables, but I still occasionally ate pizza. I just stopped eating 2,000 calories of it at a time, and kept the frequency of it to a minimum (once a week or so for 'unhealthy' food). Eating fast food less in general is a big step in the right direction, but don't cut it out completely.
Trying to realize that you really need a lifestyle change moreso than a diet is the first step to success. It's tough at first, but after you've been doing it for even a week it gets easier.
Good luck!