For fasted training, the aim is to do it on a recovery/easy/low intensity ride, not an actual training ride, therefore you won't ever come close to bonking. For yourself, with the hours you do, it is likely you are in some form of glycogen depletion state anyway. The aim of fasted training is not to get used to riding on no food. The purported benefits are growth of new mitochondria, and an increase in the % of calories from fat being used at any given (except of course high) intensity.
How would this help racing? Any gains through more mitochondria would improve performance, and being able to burn a higher % of fat, would mean saving precious glycogen. In a race, you can refuel but at most I think you are taking on 350 cal an hour at most. If say for Tokyo-Itoigawa you are riding at an average of 250W, that is a calorie burn of 900 cal an hour. Over 8 hours, that's 7,200. If you are only replacing 2,800, then you are on a 4,400 cal deficit for the ride.
Yes, preparing for the conditions you ride in and the time of day is a wise move. Here, the temperature jumps so quickly when the rainy season ends, that the earlier the adaptation starts the less I will suffer when it happens.
For an article on the thinking behind heat training, see here.
It has long been known that heat acclimation can improve performance in hot conditions (Pandolf 1988; Sawka 1996). Recently, a University of Oregon study in 2010 had trained cyclists do 10 days of heat acclimation – 100 minutes of exercise in the heat each day – and saw a 5% jump in VO2max measured in cool conditions by the end of study. In other words, heat acclimation doesn’t just make you better at dealing with heat; it makes you better, period. The researchers suggested that athletes could use this type of protocol just like they use altitude training camps, as a short-term intervention to improve performance. Training camp in the sunshine, for any race conditions!? Surely this is too good to be true!?
A recent scientific review confirmed that there is now growing evidence for the benefits of heat training on performance in both hot and cool conditions (Chalmers, Esterman 2014), suggesting a realistic and maybe superior alternative to altitude training. A New Zealand study published in 2012 used elite rowers, exercising just five days, 90 minutes per day. The rowers were in a room at 40 C and 60% humidity, and they rowed at an intensity just sufficient to keep their core temperature at a “modest” overheating level of 38.5 C. The training itself wasn’t particularly hard: the goal was to overheat the rowers, not overwork them, and the 5-day acclimation period started two weeks before a major championship competition. The result: a 1.5% increase in 2,000m rowing performance."