First, I question your strategy. Yes, it's good to get a good start to avoid traffic. But there's no reason to keep pushing beyond your realistic pace for the first lap and a half. You're just burning matches that you should save for later in the race.
Second, you shouldn't eat anything within 3 to 4 hours of the race, with the exception of 100cal or so of really easily digested carbs (i.e. gel, bloks, etc) within 15 minutes of your race. You literally should feel hungry at the line. You are eating too much, and too much fiber. Even your pre-race meal 3 to 4 hours before the race should avoid too much fiber, fat, or protein, focus on carbs. The time between meal and race allows you to digest the food, top off glycogen stores, and get insulin/sugar response back to normal.
Third, your warm-up should include some genuinely hard efforts. One way is to tackle some tricky sections of the course at race pace, another way is to do some sprints on pavement, or on the trainer. But the point is to open up your legs, get a bit of a sweat on, but not tire yourself out.