Reading all the posts I would agree that it is debatable whether you're pre-diabetic or have full blown diabetes. The good thing is that you're doing something about it.
It was only about a year ago that I was going through the same thing after my initial diagnosis. In retrospect I'm stunned how little I knew about nutrition at the time and how many foods I was eating that I thought were "healthy" but were actually shooting my BG through the roof. We've been told all our lives that fruit is healthy. For someone with impaired glucose control, it can be a disaster. Bananas, oranges, apples, pineapples, watermelon all rocket me into the 200's and 300's within minutes. The other one to be careful of is yoghurt, milk and cereal. Most commercial "low-fat" yoghurts are so fortified with sugar to make up for the flavor loss of removing fat that they contain more sugar than the equivalent portions of ice cream. Most processed foods are to be avoided. They have more hidden sugar than most people realize. Also, most artificial sweeteners in powdered form contain dextrose as a bulking agent, so if you pouring Splenda/Equal/Sweet and Low into your coffee, you'll see it raise your BG. They claim to be "Sugar Free," and technically they are if you use the strict definition of Sugar (Sucrose). However any substance ending in "ose" or "ol" will most likely raise your BG. Stevia in tablet form is the only sweetener I have found that won't.
There is so much deceptive labeling making you believe you're eating something healthy: "steel-cut, whole-grain, low-fat, net-carbs, etc." Ignore them all and only follow the real measure of truth - total carb content on labels (carbs=sugar) and your meter readings post eating these foods. I learned pretty quickly that the foods that caused the most gradual and manageable rise for me were the ones that are sold at the perimeter of the grocery store, not-processed, and usually not boxed or packaged: i.e., all non-starchy vegetables, avocados, almonds, pistachios, beef, pork, fish, chicken, sour cream, real butter, eggs, to name a few.
Regarding exercise: Different types of exercise have different effects on people. Cross training will shoot my BG from the 80's to 150's in no time. Running will bring me down about 10 points for every 30 minutes I run. Lifting weights will do the same. Mountain biking brings me up 30 points in an hour. Walking for an hour will bring me down 10 points. Everybody responds differently, so it is key to test and log what different effects different activities have and then tailor your specific exercise program accordingly. And for the ones that you love that raise your BG, you can manage with the right insulin dose. I take 1 unit of Regular Human insulin before I ride my mountain bike and keep my BG flat that way.
Regarding good books: The ones that had the greatest impact on me are: Dr. Bernstein's Diabetes Solution by Dr. Bernstein, Blood Sugar 101 and Diet 101 by Jenny Ruhl, Wheat Belly by William Davis, and Born to Run by Christopher McDougall.
All the best!