OK, I just read through the entire thread. Some comments.
BMI is a good indicator for proper weight for most people. For big men, not so much. At 6' 5" I think goal of 240 is a great number. Slow and steady weight loss is what you want, for you to lose 100 lbs. it should take you about 12-14 months. You can do it!
The oatmeal diet will not work long term. You said you've used it a couple of times, which tells me whatever you've done in the past didn't stick. Using the oatmeal plan for a couple of weeks could be a great way to jump start the weight loss, see immediate results and give you motivation. But you need a life long solution.
Weight loss is simply an easy math problem - - take in less calories than you burn and you will lose weight. You can, and should eat almost anything you want, otherwise you will get bored and revert to your old ways, and the weight comes back on.
I started a calorie counting, exercise counting plan the day after the Super Bowl last year. I am 6' 3" and I weighed 230. My goal was to get down to 205, which I attained in early June. Once I got there I decided I wanted to get under 200 (known as One-derLand) just to say I got there and because I weighed 195 when I graduated from high school, and I got there in mid-August. I weighed myself this morning and I'm at 206. So it has worked for me.
Rev, (or anyone else) if you want to know how I did it PM me and I can tell you all about it.