Well, I would say as far as diet goes you know far more than I. Especially given your diabetes so I think you are best to do whatever you and your doctor would think is best.
As for training, I would say some form of cardio a few times a week would go a long way. An ideal weight depends on a lot of factors and is highly individual. To give an example, I am 5'8" and about 205 and not overly muscular. I would say the "average person" would say I am muscular or"big" but another powerlifter would consider me average. Anyway, an ideal weight isn't as important as body composition. In other words, if you are 245 and 20% bodyfat, imagine the diference at the same weight with only 10% bodyfat. The cardio will go a long way in helping with this.
As for the weight training, go to elitefts.com and look under the exercise index section. They have descriptions of tons of exercises(some with video). Some are very much powerlifting specific but many will be helpful to you.